This fixes an issue where the theme selector on the login screen would not update its display value after selection because the component was not re-rendering. Added local state to track the current theme. Validated that this pattern is unique to the unauthenticated context.

Signed-off-by: majiayu000 <1835304752@qq.com>

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Signed-off-by: Roman Teitge <83205200+rteitge@users.noreply.github.com>

- Add HDR detection utilities for wide color gamut formats (HEIC, HEIF, WebP)
- Apply colorSpace attribute to image/video elements for HDR-capable files
- Update frontend components (AttachmentCard, PreviewImageDialog, AttachmentList)
- Expand backend thumbnail generation to support HEIC, HEIF, WebP formats
- Add Color-Gamut response headers to advertise wide gamut support
- Extend avatar MIME type validation for HDR formats

Supported formats:
- Images: HEIC, HEIF, WebP, PNG, JPEG
- Videos: MP4, QuickTime, Matroska, WebM (VP9 Profile 2)

Browser support:
- Safari 14.1+, Chrome 118+, Edge 118+
- Gracefully degrades to sRGB on unsupported browsers

- Remove shared memo-metadata folder
- Move metadata display components (AttachmentList, LocationDisplay, RelationList) to MemoView/components/metadata
- Move attachment types and utilities (LocalFile, AttachmentItem, toAttachmentItems) to MemoEditor/types/attachment
- Simplify AttachmentList and AttachmentCard to work directly with Attachment proto
- Update all imports across MemoEditor and MemoView components
- Better separation of concerns: MemoView handles display, MemoEditor handles local files + attachments

Co-authored-by: Guillaume Reichenbach <guillaume.reichenbach@reflet-digital.com>

Signed-off-by: Lynchi <77619755+Linqi1234@users.noreply.github.com>

refactor: standardize loading indicators by using Spinner for route fallbacks and specializing Skeleton for memo lists