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/breadcrumb.css

@@ -4,14 +4,14 @@
     align-items: center;
     flex-wrap: wrap;
     margin-bottom: 15px;
-    font-size: 14px;
+    font-size: var(--text-base);
     color: var(--color-text-medium);
-    gap: 2px;
+    gap: var(--space-0-5);
 }
 
 .breadcrumb-item {
-    padding: 2px 4px;
-    border-radius: 4px;
+    padding: var(--space-0-5) var(--space-1);
+    border-radius: var(--radius-sm);
     border: 2px solid transparent;
     transition:
         background 0.15s,
@@ -35,15 +35,15 @@
 }
 
 .breadcrumb-current {
-    font-weight: 600;
+    font-weight: var(--weight-semibold);
     color: var(--color-text-black);
     cursor: default;
 }
 
 .breadcrumb-separator {
-    margin: 0 4px;
+    margin: 0 var(--space-1);
     color: var(--color-text-faint);
-    font-size: 12px;
+    font-size: var(--text-xs);
     user-select: none;
 }
 
@@ -53,11 +53,11 @@
     justify-content: center;
     width: 24px;
     height: 24px;
-    border-radius: 4px;
+    border-radius: var(--radius-sm);
 }
 
 .breadcrumb-home i {
-    font-size: 12px;
+    font-size: var(--text-xs);
 }
 
 .breadcrumb-home.breadcrumb-link:hover {