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/base/animations.css

@@ -0,0 +1,18 @@
+/* ============================================================
+ * Canonical keyframes — single source for shared animations.
+ *
+ * Loaded early via main.css so every component and view reuses
+ * these by name instead of redefining them. This file replaced
+ * 6 duplicate `@keyframes spin` definitions (spinner / admin /
+ * music / photos / profile / share-public).
+ *
+ * NOTE: `oxi-spin` (icons.css) and `smdSpin` (shareModal.css) are
+ * still defined locally — folding them in needs touching their
+ * `animation-name` consumers, deferred to Fase 1.
+ * ============================================================ */
+
+@keyframes spin {
+    to {
+        transform: rotate(360deg);
+    }
+}