chore: improve metadata section UI consistency and maintainability

web/src/components/MemoView/components/metadata/AttachmentList.tsx

+import { FileIcon, PaperclipIcon } from "lucide-react";
 import { useState } from "react";
 import type { Attachment } from "@/types/proto/api/v1/attachment_service_pb";
 import { getAttachmentType, getAttachmentUrl } from "@/utils/attachment";
-import MemoAttachment from "../../../MemoAttachment";
+import { formatFileSize, getFileTypeLabel } from "@/utils/format";
 import PreviewImageDialog from "../../../PreviewImageDialog";
 import AttachmentCard from "./AttachmentCard";
+import SectionHeader from "./SectionHeader";
 
 interface AttachmentListProps {
   attachments: Attachment[];
 }
 
-function separateMediaAndDocs(attachments: Attachment[]): { media: Attachment[]; docs: Attachment[] } {
+const separateMediaAndDocs = (attachments: Attachment[]): { media: Attachment[]; docs: Attachment[] } => {
   const media: Attachment[] = [];
   const docs: Attachment[] = [];
 
@@ -23,7 +25,70 @@ function separateMediaAndDocs(attachments: Attachment[]): { media: Attachment[];
   }
 
   return { media, docs };
-}
+};
+
+const DocumentItem = ({ attachment }: { attachment: Attachment }) => {
+  const fileTypeLabel = getFileTypeLabel(attachment.type);
+  const fileSizeLabel = attachment.size ? formatFileSize(Number(attachment.size)) : undefined;
+
+  return (
+    <div className="flex items-center gap-1 px-1.5 py-1 rounded hover:bg-accent/20 transition-colors whitespace-nowrap">
+      <div className="shrink-0 w-5 h-5 rounded overflow-hidden bg-muted/40 flex items-center justify-center">
+        <FileIcon className="w-3 h-3 text-muted-foreground" />
+      </div>
+      <div className="flex items-center gap-1 min-w-0">
+        <span className="text-xs font-medium truncate" title={attachment.filename}>
+          {attachment.filename}
+        </span>
+        <div className="flex items-center gap-1 text-xs text-muted-foreground shrink-0">
+          <span className="text-muted-foreground/50">•</span>
+          <span>{fileTypeLabel}</span>
+          {fileSizeLabel && (
+            <>
+              <span className="text-muted-foreground/50">•</span>
+              <span>{fileSizeLabel}</span>
+            </>
+          )}
+        </div>
+      </div>
+    </div>
+  );
+};
+
+const MediaGrid = ({ attachments, onImageClick }: { attachments: Attachment[]; onImageClick: (url: string) => void }) => (
+  <div className="grid grid-cols-2 md:grid-cols-3 lg:grid-cols-4 gap-2">
+    {attachments.map((attachment) => (
+      <div
+        key={attachment.name}
+        className="aspect-square rounded-lg overflow-hidden bg-muted/40 border border-border hover:border-accent/50 transition-all cursor-pointer group"
+        onClick={() => onImageClick(getAttachmentUrl(attachment))}
+      >
+        <div className="w-full h-full relative">
+          <AttachmentCard attachment={attachment} className="rounded-none" />
+          {getAttachmentType(attachment) === "video/*" && (
+            <div className="absolute inset-0 flex items-center justify-center bg-black/30 group-hover:bg-black/40 transition-colors">
+              <div className="w-8 h-8 rounded-full bg-white/80 flex items-center justify-center">
+                <svg className="w-5 h-5 text-black fill-current ml-0.5" viewBox="0 0 24 24">
+                  <path d="M8 5v14l11-7z" />
+                </svg>
+              </div>
+            </div>
+          )}
+        </div>
+      </div>
+    ))}
+  </div>
+);
+
+const DocsList = ({ attachments }: { attachments: Attachment[] }) => (
+  <div className="flex flex-col gap-0.5">
+    {attachments.map((attachment) => (
+      <a key={attachment.name} href={getAttachmentUrl(attachment)} download title={`Download ${attachment.filename}`}>
+        <DocumentItem attachment={attachment} />
+      </a>
+    ))}
+  </div>
+);
 
 const AttachmentList = ({ attachments }: AttachmentListProps) => {
   const [previewImage, setPreviewImage] = useState<{ open: boolean; urls: string[]; index: number; mimeType?: string }>({
@@ -33,45 +98,33 @@ const AttachmentList = ({ attachments }: AttachmentListProps) => {
     mimeType: undefined,
   });
 
-  const handleImageClick = (imgUrl: string, mediaAttachments: Attachment[]) => {
-    const imageAttachments = mediaAttachments.filter((attachment) => getAttachmentType(attachment) === "image/*");
-    const imgUrls = imageAttachments.map((attachment) => getAttachmentUrl(attachment));
-    const index = imgUrls.findIndex((url) => url === imgUrl);
-    const mimeType = imageAttachments[index]?.type;
-    setPreviewImage({ open: true, urls: imgUrls, index, mimeType });
-  };
-
   const { media: mediaItems, docs: docItems } = separateMediaAndDocs(attachments);
 
   if (attachments.length === 0) {
     return null;
   }
 
+  const handleImageClick = (imgUrl: string) => {
+    const imageAttachments = mediaItems.filter((a) => getAttachmentType(a) === "image/*");
+    const imgUrls = imageAttachments.map((a) => getAttachmentUrl(a));
+    const index = imgUrls.findIndex((url) => url === imgUrl);
+    const mimeType = imageAttachments[index]?.type;
+    setPreviewImage({ open: true, urls: imgUrls, index, mimeType });
+  };
+
   return (
     <>
-      {mediaItems.length > 0 && (
-        <div className="w-full flex flex-row justify-start overflow-auto gap-2">
-          {mediaItems.map((attachment) => (
-            <div key={attachment.name} className="max-w-[60%] w-fit flex flex-col justify-start items-start shrink-0">
-              <AttachmentCard
-                attachment={attachment}
-                onClick={() => {
-                  handleImageClick(getAttachmentUrl(attachment), mediaItems);
-                }}
-                className="max-h-64 grow"
-              />
-            </div>
-          ))}
-        </div>
-      )}
+      <div className="w-full rounded-lg border border-border bg-muted/20 overflow-hidden">
+        <SectionHeader icon={PaperclipIcon} title="Attachments" count={attachments.length} />
 
-      {docItems.length > 0 && (
-        <div className="w-full flex flex-row justify-start overflow-auto gap-2">
-          {docItems.map((attachment) => (
-            <MemoAttachment key={attachment.name} attachment={attachment} />
-          ))}
+        <div className="p-2 flex flex-col gap-1">
+          {mediaItems.length > 0 && <MediaGrid attachments={mediaItems} onImageClick={handleImageClick} />}
+
+          {mediaItems.length > 0 && docItems.length > 0 && <div className="border-t border-border opacity-60" />}
+
+          {docItems.length > 0 && <DocsList attachments={docItems} />}
+        </div>
       </div>
-      )}
 
       <PreviewImageDialog
         open={previewImage.open}

web/src/components/MemoView/components/metadata/MetadataCard.tsx

-import { ReactNode } from "react";
-import { cn } from "@/lib/utils";
-
-interface MetadataCardProps {
-  children: ReactNode;
-  className?: string;
-}
-
-const MetadataCard = ({ children, className }: MetadataCardProps) => {
-  return (
-    <div
-      className={cn(
-        "relative flex flex-col justify-start items-start w-full px-2 pt-2 pb-1.5 bg-muted/50 rounded-lg border border-border",
-        className,
-      )}
-    >
-      {children}
-    </div>
-  );
-};
-
-export default MetadataCard;

web/src/components/MemoView/components/metadata/RelationCard.tsx

@@ -15,14 +15,16 @@ const RelationCard = ({ memo, parentPage, className }: RelationCardProps) => {
   return (
     <Link
       className={cn(
-        "w-full flex flex-row justify-start items-center text-sm leading-5 text-muted-foreground hover:text-foreground hover:bg-accent rounded px-1 py-1 transition-colors",
+        "flex items-center gap-1 px-1 py-1 rounded text-xs text-muted-foreground hover:text-foreground hover:bg-accent/20 transition-colors group",
         className,
       )}
       to={`/${memo.name}`}
       viewTransition
       state={{ from: parentPage }}
     >
-      <span className="text-[10px] opacity-60 leading-4 border border-border font-mono px-1 rounded-full mr-1">{memoId.slice(0, 6)}</span>
+      <span className="text-[8px] font-mono px-1 py-0.5 rounded border border-border bg-muted/40 group-hover:bg-accent/30 transition-colors shrink-0">
+        {memoId.slice(0, 6)}
+      </span>
       <span className="truncate">{memo.snippet}</span>
     </Link>
   );

web/src/components/MemoView/components/metadata/RelationList.tsx

 import { LinkIcon, MilestoneIcon } from "lucide-react";
-import { useState } from "react";
+import { useMemo, useState } from "react";
 import { cn } from "@/lib/utils";
 import type { MemoRelation } from "@/types/proto/api/v1/memo_service_pb";
 import { MemoRelation_Type } from "@/types/proto/api/v1/memo_service_pb";
 import { useTranslate } from "@/utils/i18n";
-import MetadataCard from "./MetadataCard";
 import RelationCard from "./RelationCard";
+import SectionHeader from "./SectionHeader";
 
 interface RelationListProps {
   relations: MemoRelation[];
@@ -16,75 +16,68 @@ interface RelationListProps {
 
 function RelationList({ relations, currentMemoName, parentPage, className }: RelationListProps) {
   const t = useTranslate();
-  const [selectedTab, setSelectedTab] = useState<"referencing" | "referenced">("referencing");
+  const [activeTab, setActiveTab] = useState<"referencing" | "referenced">("referencing");
 
-  const referencingRelations = relations.filter(
-    (relation) =>
-      relation.type === MemoRelation_Type.REFERENCE &&
-      relation.memo?.name === currentMemoName &&
-      relation.relatedMemo?.name !== currentMemoName,
-  );
-
-  const referencedRelations = relations.filter(
-    (relation) =>
-      relation.type === MemoRelation_Type.REFERENCE &&
-      relation.memo?.name !== currentMemoName &&
-      relation.relatedMemo?.name === currentMemoName,
-  );
+  const { referencingRelations, referencedRelations } = useMemo(() => {
+    return {
+      referencingRelations: relations.filter(
+        (r) => r.type === MemoRelation_Type.REFERENCE && r.memo?.name === currentMemoName && r.relatedMemo?.name !== currentMemoName,
+      ),
+      referencedRelations: relations.filter(
+        (r) => r.type === MemoRelation_Type.REFERENCE && r.memo?.name !== currentMemoName && r.relatedMemo?.name === currentMemoName,
+      ),
+    };
+  }, [relations, currentMemoName]);
 
   if (referencingRelations.length === 0 && referencedRelations.length === 0) {
     return null;
   }
 
-  const activeTab = referencingRelations.length === 0 ? "referenced" : selectedTab;
+  const hasBothTabs = referencingRelations.length > 0 && referencedRelations.length > 0;
+  const defaultTab = referencingRelations.length > 0 ? "referencing" : "referenced";
+  const tab = hasBothTabs ? activeTab : defaultTab;
+  const isReferencing = tab === "referencing";
+  const icon = isReferencing ? LinkIcon : MilestoneIcon;
+  const activeRelations = isReferencing ? referencingRelations : referencedRelations;
 
   return (
-    <MetadataCard className={className}>
-      <div className="w-full flex flex-row justify-start items-center mb-1 gap-3 opacity-60">
-        {referencingRelations.length > 0 && (
-          <button
-            className={cn(
-              "w-auto flex flex-row justify-start items-center text-xs gap-0.5 text-muted-foreground hover:text-foreground hover:bg-accent rounded px-1 py-0.5 transition-colors",
-              activeTab === "referencing" && "text-foreground bg-accent",
-            )}
-            onClick={() => setSelectedTab("referencing")}
-          >
-            <LinkIcon className="w-3 h-auto shrink-0 opacity-70" />
-            <span>{t("common.referencing")}</span>
-            <span className="opacity-80">({referencingRelations.length})</span>
-          </button>
-        )}
-        {referencedRelations.length > 0 && (
-          <button
-            className={cn(
-              "w-auto flex flex-row justify-start items-center text-xs gap-0.5 text-muted-foreground hover:text-foreground hover:bg-accent rounded px-1 py-0.5 transition-colors",
-              activeTab === "referenced" && "text-foreground bg-accent",
-            )}
-            onClick={() => setSelectedTab("referenced")}
-          >
-            <MilestoneIcon className="w-3 h-auto shrink-0 opacity-70" />
-            <span>{t("common.referenced-by")}</span>
-            <span className="opacity-80">({referencedRelations.length})</span>
-          </button>
-        )}
-      </div>
+    <div className={cn("w-full rounded-lg border border-border bg-muted/20 overflow-hidden", className)}>
+      <SectionHeader
+        icon={icon}
+        title={isReferencing ? t("common.referencing") : t("common.referenced-by")}
+        count={activeRelations.length}
+        tabs={
+          hasBothTabs
+            ? [
+                {
+                  id: "referencing",
+                  label: t("common.referencing"),
+                  count: referencingRelations.length,
+                  active: isReferencing,
+                  onClick: () => setActiveTab("referencing"),
+                },
+                {
+                  id: "referenced",
+                  label: t("common.referenced-by"),
+                  count: referencedRelations.length,
+                  active: !isReferencing,
+                  onClick: () => setActiveTab("referenced"),
+                },
+              ]
+            : undefined
+        }
+      />
 
-      {activeTab === "referencing" && referencingRelations.length > 0 && (
-        <div className="w-full flex flex-col justify-start items-start">
-          {referencingRelations.map((relation) => (
-            <RelationCard key={relation.relatedMemo!.name} memo={relation.relatedMemo!} parentPage={parentPage} />
+      <div className="p-1.5 flex flex-col gap-0">
+        {activeRelations.map((relation) => (
+          <RelationCard
+            key={isReferencing ? relation.relatedMemo!.name : relation.memo!.name}
+            memo={isReferencing ? relation.relatedMemo! : relation.memo!}
+            parentPage={parentPage}
+          />
         ))}
       </div>
-      )}
-
-      {activeTab === "referenced" && referencedRelations.length > 0 && (
-        <div className="w-full flex flex-col justify-start items-start">
-          {referencedRelations.map((relation) => (
-            <RelationCard key={relation.memo!.name} memo={relation.memo!} parentPage={parentPage} />
-          ))}
     </div>
-      )}
-    </MetadataCard>
   );
 }
 

web/src/components/MemoView/components/metadata/SectionHeader.tsx

+import { LucideIcon } from "lucide-react";
+import { cn } from "@/lib/utils";
+
+interface SectionHeaderProps {
+  icon: LucideIcon;
+  title: string;
+  count: number;
+  tabs?: Array<{
+    id: string;
+    label: string;
+    count: number;
+    active: boolean;
+    onClick: () => void;
+  }>;
+}
+
+const SectionHeader = ({ icon: Icon, title, count, tabs }: SectionHeaderProps) => {
+  return (
+    <div className="flex items-center gap-1.5 px-2 py-1 border-b border-border bg-muted/30">
+      <Icon className="w-3.5 h-3.5 text-muted-foreground" />
+
+      {tabs && tabs.length > 1 ? (
+        <div className="flex items-center gap-0.5">
+          {tabs.map((tab, idx) => (
+            <div key={tab.id} className="flex items-center gap-0.5">
+              <button
+                onClick={tab.onClick}
+                className={cn(
+                  "text-xs font-medium px-0 py-0 transition-colors",
+                  tab.active ? "text-foreground" : "text-muted-foreground hover:text-foreground",
+                )}
+              >
+                {tab.label}({tab.count})
+              </button>
+              {idx < tabs.length - 1 && <span className="text-muted-foreground/50">/</span>}
+            </div>
+          ))}
+        </div>
+      ) : (
+        <span className="text-xs font-medium text-foreground">
+          {title} ({count})
+        </span>
+      )}
+    </div>
+  );
+};
+
+export default SectionHeader;

web/src/components/MemoView/components/metadata/index.ts

 export { default as AttachmentCard } from "./AttachmentCard";
 export { default as AttachmentList } from "./AttachmentList";
 export { default as LocationDisplay } from "./LocationDisplay";
-export { default as MetadataCard } from "./MetadataCard";
+
 export { default as RelationCard } from "./RelationCard";
 export { default as RelationList } from "./RelationList";