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/components/shareDialog.css

@@ -12,13 +12,13 @@
 
 .existing-share-item {
     background-color: var(--color-bg-subtle);
-    border-radius: 4px;
-    padding: 10px;
-    margin-bottom: 10px;
+    border-radius: var(--radius-sm);
+    padding: var(--space-2-5);
+    margin-bottom: var(--space-2-5);
 }
 
 .share-url {
-    font-size: 12px;
+    font-size: var(--text-xs);
     overflow: hidden;
     text-overflow: ellipsis;
     white-space: nowrap;
@@ -27,10 +27,10 @@
 }
 
 .share-info {
-    font-size: 11px;
+    font-size: var(--text-2xs);
     display: flex;
     gap: 15px;
-    margin-bottom: 10px;
+    margin-bottom: var(--space-2-5);
     color: var(--color-share-owner-text);
 }
 
@@ -50,19 +50,19 @@
 
 .share-link-actions {
     display: flex;
-    gap: 10px;
+    gap: var(--space-2-5);
     margin-top: 5px;
 }
 
 .btn-small {
-    font-size: 12px;
-    padding: 5px 10px;
+    font-size: var(--text-xs);
+    padding: 5px var(--space-2-5);
 }
 
 #notification-message {
     width: 100%;
-    padding: 10px;
+    padding: var(--space-2-5);
     border: 1px solid var(--color-border-ddd);
-    border-radius: 4px;
+    border-radius: var(--radius-sm);
     resize: vertical;
 }