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/js/core/errorBoundary.js

@@ -0,0 +1,39 @@
+// Global error boundary.
+//
+// Surfaces uncaught errors and unhandled promise rejections as a terse,
+// throttled toast instead of failing silently — the full detail always goes to
+// the console. Intentionally dependency-free so an error handler can never
+// itself fail to load.
+
+let lastShown = 0;
+
+/** @param {string} message */
+function showToast(message) {
+    const now = Date.now();
+    if (now - lastShown < 4000) return; // throttle bursts of related errors
+    lastShown = now;
+
+    const el = document.createElement('div');
+    el.className = 'error-toast';
+    el.setAttribute('role', 'alert');
+    el.textContent = message;
+    document.body.appendChild(el);
+
+    requestAnimationFrame(() => el.classList.add('is-visible'));
+    setTimeout(() => {
+        el.classList.remove('is-visible');
+        setTimeout(() => el.remove(), 300);
+    }, 5000);
+}
+
+const GENERIC = 'Something went wrong. Please try again.';
+
+window.addEventListener('error', (event) => {
+    console.error('[error-boundary]', event.error || event.message);
+    showToast(GENERIC);
+});
+
+window.addEventListener('unhandledrejection', (event) => {
+    console.error('[error-boundary] unhandled rejection:', event.reason);
+    showToast(GENERIC);
+});