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/views/device-verify.css

@@ -6,18 +6,19 @@
 }
 body {
     font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
-    background: var(--color-bg-hover);
+    /* Shared brand backdrop (centralised in --brand-ambient). */
+    background: var(--brand-ambient);
     color: var(--color-text-heading);
     display: flex;
     justify-content: center;
     align-items: center;
-    min-height: 100vh;
+    min-height: 100dvh;
     padding: 1rem;
 }
 .dag-card {
     background: var(--color-bg-surface);
-    border-radius: var(--radius, 12px);
-    box-shadow: 0 4px 24px var(--color-shadow-sm);
+    border-radius: var(--radius-3xl);
+    box-shadow: var(--shadow-xl);
     padding: 2.5rem;
     max-width: 440px;
     width: 100%;
@@ -27,8 +28,8 @@ body {
     margin-bottom: 1.5rem;
 }
 .dag-logo h1 {
-    font-size: 1.5rem;
-    font-weight: 700;
+    font-size: var(--text-2xl);
+    font-weight: var(--weight-bold);
 }
 .dag-logo span {
     color: var(--color-primary);
@@ -44,7 +45,7 @@ p.subtitle {
 }
 label {
     display: block;
-    font-weight: 600;
+    font-weight: var(--weight-semibold);
     font-size: 0.85rem;
     margin-bottom: 0.4rem;
 }
@@ -56,7 +57,7 @@ input[type="text"] {
     text-align: center;
     text-transform: uppercase;
     border: 2px solid var(--color-border);
-    border-radius: 8px;
+    border-radius: var(--radius-lg);
     outline: none;
     transition: border-color 0.2s;
 }
@@ -65,7 +66,7 @@ input[type="text"]:focus {
 }
 .device-info {
     background: var(--color-border-light);
-    border-radius: 8px;
+    border-radius: var(--radius-lg);
     padding: 1rem;
     margin: 1rem 0;
 }
@@ -79,7 +80,7 @@ input[type="text"]:focus {
     font-size: 0.85rem;
 }
 .device-info .value {
-    font-weight: 600;
+    font-weight: var(--weight-semibold);
     font-size: 0.85rem;
 }
 .actions {
@@ -91,22 +92,22 @@ button {
     flex: 1;
     padding: 0.75rem;
     border: none;
-    border-radius: 8px;
+    border-radius: var(--radius-lg);
     font-size: 0.95rem;
-    font-weight: 600;
+    font-weight: var(--weight-semibold);
     cursor: pointer;
     transition: background 0.2s;
 }
 .btn-approve {
     background: var(--color-primary);
-    color: var(--color-danger-text);
+    color: var(--color-on-accent);
 }
 .btn-approve:hover {
     background: var(--color-primary-hover);
 }
 .btn-deny {
-    background: var(--color-error-text);
-    color: var(--color-danger-text);
+    background: var(--color-danger-bg);
+    color: var(--color-on-accent);
 }
 .btn-deny:hover {
     background: var(--color-danger-bg-hover);
@@ -118,9 +119,9 @@ button:disabled {
 .status {
     text-align: center;
     padding: 1rem;
-    border-radius: 8px;
+    border-radius: var(--radius-lg);
     margin-top: 1rem;
-    font-weight: 600;
+    font-weight: var(--weight-semibold);
 }
 .status.success {
     background: var(--color-success-bg);