fix(web): fix explore page showing private tags and improve stats hook

The explore page sidebar was showing tags from the current user's private
memos because the default ListMemos query applies a server-side OR filter
(creator_id == X || visibility in [...]), mixing private content in.

Fix by using a visibility-scoped ListMemos request in the explore context
so private memos are always excluded via the AND'd server auth filter.

Also consolidate two always-firing useMemos calls into one context-aware
query, unify activity stats computation with countBy across all branches,
and extract a toDateString helper to remove duplicated formatting logic.

web/src/components/StatisticsView/MonthNavigator.tsx

 import dayjs from "dayjs";
 import { ChevronLeftIcon, ChevronRightIcon } from "lucide-react";
 import { memo, useCallback, useMemo, useState } from "react";
+import { useTranslation } from "react-i18next";
 import { YearCalendar } from "@/components/ActivityCalendar";
 import { Button } from "@/components/ui/button";
 import { Dialog, DialogContent, DialogTitle, DialogTrigger } from "@/components/ui/dialog";
-import { useTranslation } from "react-i18next";
 import { addMonths, formatMonth, getMonthFromDate, getYearFromDate, setYearAndMonth } from "@/lib/calendar-utils";
 import type { MonthNavigatorProps } from "@/types/statistics";
 
@@ -21,7 +21,10 @@ export const MonthNavigator = memo(({ visibleMonth, onMonthChange, activityStats
     [visibleMonth],
   );
 
-  const monthLabel = useMemo(() => currentMonth.toLocaleString(i18n.language, { year: "numeric", month: "long" }), [currentMonth, i18n.language]);
+  const monthLabel = useMemo(
+    () => currentMonth.toLocaleString(i18n.language, { year: "numeric", month: "long" }),
+    [currentMonth, i18n.language],
+  );
 
   const handlePrevMonth = useCallback(() => onMonthChange(addMonths(visibleMonth, -1)), [visibleMonth, onMonthChange]);
   const handleNextMonth = useCallback(() => onMonthChange(addMonths(visibleMonth, 1)), [visibleMonth, onMonthChange]);

web/src/hooks/useFilteredMemoStats.ts

@@ -2,6 +2,8 @@ import { timestampDate } from "@bufbuild/protobuf/wkt";
 import dayjs from "dayjs";
 import { countBy } from "lodash-es";
 import { useMemo } from "react";
+import type { MemoExplorerContext } from "@/components/MemoExplorer";
+import useCurrentUser from "@/hooks/useCurrentUser";
 import { useMemos } from "@/hooks/useMemoQueries";
 import { useUserStats } from "@/hooks/useUserQueries";
 import type { StatisticsData } from "@/types/statistics";
@@ -14,66 +16,72 @@ export interface FilteredMemoStats {
 
 export interface UseFilteredMemoStatsOptions {
   userName?: string;
+  context?: MemoExplorerContext;
 }
 
+const toDateString = (date: Date) => dayjs(date).format("YYYY-MM-DD");
+
 export const useFilteredMemoStats = (options: UseFilteredMemoStatsOptions = {}): FilteredMemoStats => {
-  const { userName } = options;
+  const { userName, context } = options;
+  const currentUser = useCurrentUser();
 
-  // Fetch user stats if userName is provided
+  // home/profile: use backend per-user stats (full tag set, not page-limited)
   const { data: userStats, isLoading: isLoadingUserStats } = useUserStats(userName);
 
-  // Fetch memos for fallback computation (or when userName is not provided)
-  const { data: memosResponse, isLoading: isLoadingMemos } = useMemos({});
+  // explore: fetch memos with visibility filter to exclude private content.
+  // ListMemos AND's the request filter with the server's auth filter, so private
+  // memos are always excluded regardless of backend version.
+  // other contexts: fetch with default params for the fallback memo-based path.
+  const exploreVisibilityFilter = currentUser != null ? 'visibility in ["PUBLIC", "PROTECTED"]' : 'visibility in ["PUBLIC"]';
+  const memoQueryParams = context === "explore" ? { filter: exploreVisibilityFilter, pageSize: 1000 } : {};
+  const { data: memosResponse, isLoading: isLoadingMemos } = useMemos(memoQueryParams);
 
   const data = useMemo(() => {
     const loading = isLoadingUserStats || isLoadingMemos;
     let activityStats: Record<string, number> = {};
     let tagCount: Record<string, number> = {};
 
-    // Try to use backend user stats if userName is provided and available
-    if (userName && userStats) {
-      // Use activity timestamps from user stats
+    if (context === "explore") {
+      // Tags and activity stats from visibility-filtered memos (no private content).
+      for (const memo of memosResponse?.memos ?? []) {
+        for (const tag of memo.tags ?? []) {
+          tagCount[tag] = (tagCount[tag] ?? 0) + 1;
+        }
+      }
+      const displayDates = (memosResponse?.memos ?? [])
+        .map((memo) => (memo.displayTime ? timestampDate(memo.displayTime) : undefined))
+        .filter((date): date is Date => date !== undefined)
+        .map(toDateString);
+      activityStats = countBy(displayDates);
+    } else if (userName && userStats) {
+      // home/profile: use backend per-user stats
       if (userStats.memoDisplayTimestamps && userStats.memoDisplayTimestamps.length > 0) {
         activityStats = countBy(
           userStats.memoDisplayTimestamps
             .map((ts) => (ts ? timestampDate(ts) : undefined))
             .filter((date): date is Date => date !== undefined)
-            .map((date) => dayjs(date).format("YYYY-MM-DD")),
+            .map(toDateString),
         );
       }
-      // Use tag counts from user stats
       if (userStats.tagCount) {
         tagCount = userStats.tagCount;
       }
     } else if (memosResponse?.memos) {
-      // Fallback: compute from memos if backend stats not available
-      // Also used for Explore and Archived contexts
-      const displayTimeList: Date[] = [];
-      const memos = memosResponse.memos;
-
-      for (const memo of memos) {
-        // Collect display timestamps for activity calendar
-        const displayTime = memo.displayTime ? timestampDate(memo.displayTime) : undefined;
-        if (displayTime) {
-          displayTimeList.push(displayTime);
-        }
-        // Count tags
-        if (memo.tags && memo.tags.length > 0) {
-          for (const tag of memo.tags) {
+      // archived/fallback: compute from cached memos
+      const displayDates = memosResponse.memos
+        .map((memo) => (memo.displayTime ? timestampDate(memo.displayTime) : undefined))
+        .filter((date): date is Date => date !== undefined)
+        .map(toDateString);
+      activityStats = countBy(displayDates);
+      for (const memo of memosResponse.memos) {
+        for (const tag of memo.tags ?? []) {
           tagCount[tag] = (tagCount[tag] || 0) + 1;
         }
       }
     }
 
-      activityStats = countBy(displayTimeList.map((date) => dayjs(date).format("YYYY-MM-DD")));
-    }
-
-    return {
-      statistics: { activityStats },
-      tags: tagCount,
-      loading,
-    };
-  }, [userName, userStats, memosResponse, isLoadingUserStats, isLoadingMemos]);
+    return { statistics: { activityStats }, tags: tagCount, loading };
+  }, [context, userName, userStats, memosResponse, isLoadingUserStats, isLoadingMemos]);
 
   return data;
 };

web/src/layouts/MainLayout.tsx

@@ -49,23 +49,17 @@ const MainLayout = () => {
     }
   }, [location.pathname, context]);
 
-  // Determine which user name to use for stats
-  // - home: current user (uses backend user stats for normal memos)
-  // - profile: viewed user (uses backend user stats for normal memos)
-  // - archived: undefined (compute from cached archived memos, since user stats only includes normal memos)
-  // - explore: undefined (compute from cached memos)
+  // Determine which user name to use for per-user stats.
+  // - home: current user's stats
+  // - profile: viewed user's stats
+  // - archived/explore: no user scope (each handled differently inside the hook)
   const statsUserName = useMemo(() => {
-    if (context === "home") {
-      return currentUser?.name;
-    } else if (context === "profile") {
-      return profileUserName;
-    }
-    return undefined; // archived and explore contexts compute from cache
+    if (context === "home") return currentUser?.name;
+    if (context === "profile") return profileUserName;
+    return undefined;
   }, [context, currentUser, profileUserName]);
 
-  // Fetch stats from memo store cache (populated by PagedMemoList)
-  // For user-scoped contexts, use backend user stats for tags (unaffected by filters)
-  const { statistics, tags } = useFilteredMemoStats({ userName: statsUserName });
+  const { statistics, tags } = useFilteredMemoStats({ userName: statsUserName, context });
 
   return (
     <section className="@container w-full min-h-full flex flex-col justify-start items-center">