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/itemTooltip.css

@@ -18,11 +18,11 @@
     display: grid;
     grid-template-columns: 1em max-content 1fr;
     column-gap: 0.6em;
-    row-gap: 6px;
+    row-gap: var(--space-1-5);
     align-items: center;
 
     color: var(--color-text-muted);
-    font-size: 0.75rem;
+    font-size: var(--text-xs);
 
     pointer-events: none;
 
@@ -51,7 +51,7 @@
 
 /* Label column */
 .path-tooltip__label {
-    font-weight: 600;
+    font-weight: var(--weight-semibold);
     color: var(--color-text-secondary);
     white-space: nowrap;
 }
@@ -88,5 +88,5 @@
 }
 
 .path-tooltip .user-vignette__name {
-    font-size: 0.75rem;
+    font-size: var(--text-xs);
 }