feat: photo/video capture-date pipeline + premium UI/UX overhaul

Backend — Photos timeline now groups by real capture date instead of upload time. New MediaMetadataService (FileLifecycleHook) extracts EXIF DateTimeOriginal from images and container creation_time from videos (mov/mp4/mkv) via nom-exif, timezone-correct (OffsetTimeOriginal), persisting captured_at so the existing media_sort_date trigger takes over. Adds POST /admin/photos/metadata/reextract to backfill existing media. Falls back to upload date when no embedded date exists.

Frontend — premium grid cards: combined metadata line (relative date · size, owner avatar when shared), custom selection checkbox with a clear checked state, uniform full-width 4:3 thumbnail tiles independent of filename length, centered file-type icons, and a hit-test fix so checkbox/star/kebab clicks reach the controls (the decorative thumbnail no longer captures pointer events). Notification messages internationalised across all 16 locales. Broader polish: design tokens, a11y/focus-visible states, brand + PWA assets.

Chore — bump semver-compatible dependencies (cargo upgrade); add nom-exif 3.6.1.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

static/css/views/favorites.css

@@ -48,20 +48,20 @@
     flex-direction: column;
     align-items: center;
     justify-content: center;
-    padding: 50px 20px;
+    padding: 50px var(--space-5);
     text-align: center;
     color: var(--color-text-gray);
 }
 
 .favorites-empty-state i {
-    font-size: 48px;
+    font-size: var(--text-6xl);
     color: var(--color-warning-text);
-    margin-bottom: 20px;
+    margin-bottom: var(--space-5);
     opacity: 0.6;
 }
 
 .favorites-empty-state p {
-    margin-bottom: 10px;
+    margin-bottom: var(--space-2-5);
     max-width: 400px;
 }
 
@@ -98,13 +98,13 @@
 /* List view: small star next to the name */
 .favorite-star-inline {
     color: var(--color-warning-text);
-    font-size: 11px;
-    margin-left: 6px;
+    font-size: var(--text-2xs);
+    margin-left: var(--space-1-5);
     vertical-align: middle;
     filter: drop-shadow(0 0 1px var(--color-device-verify-drop-shadow));
 
     [dir="rtl"] & {
         margin-left: 0;
-        margin-right: 6px;
+        margin-right: var(--space-1-5);
     }
 }