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/sharing/fileSharing.js

@@ -8,6 +8,7 @@ import { switchToSharedSection } from '../../app/navigation.js';
 import { ui } from '../../app/ui.js';
 import { getCsrfHeaders } from '../../core/csrf.js';
 import { formatDateTime } from '../../core/formatters.js';
+import { i18n } from '../../core/i18n.js';
 
 /**
  * @import {CreateShare, ShareItem, UpdateShare} from '../../core/types.js'
@@ -169,11 +170,11 @@ const fileSharing = {
     async copyLinkToClipboard(url) {
         try {
             await navigator.clipboard.writeText(url);
-            ui.showNotification('Link copied', 'Link copied to clipboard');
+            ui.showNotification(i18n.t('notif.linkCopied'), i18n.t('notif.linkCopiedBody'));
             return true;
         } catch (error) {
             console.error('Error copying to clipboard:', error);
-            ui.showNotification('Error', 'Could not copy link');
+            ui.showNotification(i18n.t('notif.errorTitle'), i18n.t('notif.linkCopyError'));
             return false;
         }
     },
@@ -198,7 +199,7 @@ const fileSharing = {
     async sendShareNotification(shareUrl, recipientEmail, _message = '') {
         // TODO: implement backend endpoint for email notifications
         console.log(`Share notification for ${shareUrl} sent to ${recipientEmail}`);
-        ui.showNotification('Notification sent', `Notification sent to ${recipientEmail}`);
+        ui.showNotification(i18n.t('notif.notificationSent'), i18n.t('notif.notificationSentBody', { email: recipientEmail }));
         return true;
     },