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/linkChip.css

@@ -9,12 +9,12 @@
     align-items: center;
     gap: 5px;
     max-width: 100%;
-    padding: 2px 0;
+    padding: var(--space-0-5) 0;
     border: none;
     background: transparent;
     color: var(--color-text);
     cursor: pointer;
-    font-size: 13px;
+    font-size: var(--text-sm);
     text-align: left;
     transition: color 0.12s;
 }
@@ -29,7 +29,7 @@
 }
 
 .link-chip__icon {
-    font-size: 12px;
+    font-size: var(--text-xs);
     color: var(--color-text-faint);
     flex-shrink: 0;
     transition: color 0.12s;