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/features/files/contextMenus.js

@@ -744,14 +744,14 @@ const contextMenus = {
         const shareUrl = app.notificationShareUrl;
 
         if (!email || !shareUrl) {
-            ui.showNotification('Error', 'Please enter a valid email address');
+            ui.showNotification(i18n.t('notif.errorTitle'), i18n.t('notif.invalidEmail'));
             return;
         }
 
         // Validate email format
         const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
         if (!emailRegex.test(email)) {
-            ui.showNotification('Error', 'Please enter a valid email address');
+            ui.showNotification(i18n.t('notif.errorTitle'), i18n.t('notif.invalidEmail'));
             return;
         }
 
@@ -760,7 +760,7 @@ const contextMenus = {
             document.getElementById('notification-dialog')?.classList.add('hidden');
         } catch (error) {
             console.error('Error sending notification:', error);
-            ui.showNotification('Error', 'Could not send notification');
+            ui.showNotification(i18n.t('notif.errorTitle'), i18n.t('notif.notificationSendError'));
         }
     },