feat: 0.1.1 — timeline scrubber, gallery virtualisation, folder reorder, QoL polish

Timeline:
- Add a right-edge scrubber (year labels + month dots) that jumps to any
  period; runs in the same direction as the scrolled content
- Load the full filtered set in Timeline view so the scrubber spans the whole
  library instead of just the first page

Gallery & UI:
- Virtualise the gallery grid
- Folder reordering in the sidebar (drag + persisted sort_order) and a themed
  dropdown component
- Subtle Light theme contrast fixes for toggles, secondary buttons and the
  update toast

Embedding workers now defer video jobs without a thumbnail at claim time and
requeue any previously-failed deferred jobs on startup, so videos no longer
churn through failed embeddings.

QoL polish across BackgroundTasks, DuplicateFinder, Lightbox and VideoPlayer.

src/index.css

@@ -1,5 +1,7 @@
 @import "tailwindcss";
 
+@custom-variant light-theme (&:is(html[data-theme="subtle-light"] *));
+
 * {
   box-sizing: border-box;
 }
@@ -10,11 +12,55 @@ body,
   height: 100%;
   margin: 0;
   padding: 0;
-  background: #030712;
+  background: var(--color-gray-950);
   font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
   -webkit-font-smoothing: antialiased;
 }
 
+html[data-theme="conventional-dark"] {
+  --color-gray-950: #1f1f1f;
+  --color-gray-900: #252525;
+  --color-gray-800: #303030;
+  --color-gray-700: #444444;
+  --color-gray-600: #666666;
+  --color-gray-500: #858585;
+  --color-gray-400: #a3a3a3;
+  --color-gray-300: #c4c4c4;
+  --color-gray-200: #dddddd;
+  --color-gray-100: #eeeeee;
+  background: #1f1f1f;
+}
+
+html[data-theme="subtle-light"] {
+  --color-white: #18202c;
+  --color-gray-950: #e9e7e2;
+  --color-gray-900: #dedbd4;
+  --color-gray-800: #cfcbc3;
+  --color-gray-700: #aea99f;
+  --color-gray-600: #817b72;
+  --color-gray-500: #655f57;
+  --color-gray-400: #514b44;
+  --color-gray-300: #403b35;
+  --color-gray-200: #302c28;
+  --color-gray-100: #24211e;
+  background: #e9e7e2;
+}
+
+html[data-theme="subtle-light"] .media-dark-surface {
+  --color-white: #ffffff;
+  --color-black: #000000;
+  --color-gray-950: #030712;
+  --color-gray-900: #111827;
+  --color-gray-800: #1f2937;
+  --color-gray-700: #374151;
+  --color-gray-600: #4b5563;
+  --color-gray-500: #6b7280;
+  --color-gray-400: #9ca3af;
+  --color-gray-300: #d1d5db;
+  --color-gray-200: #e5e7eb;
+  --color-gray-100: #f3f4f6;
+}
+
 /* Custom scrollbar */
 ::-webkit-scrollbar {
   width: 6px;
@@ -24,9 +70,9 @@ body,
   background: transparent;
 }
 ::-webkit-scrollbar-thumb {
-  background: rgba(255, 255, 255, 0.1);
+  background: color-mix(in srgb, var(--color-white, #fff) 12%, transparent);
   border-radius: 3px;
 }
 ::-webkit-scrollbar-thumb:hover {
-  background: rgba(255, 255, 255, 0.2);
+  background: color-mix(in srgb, var(--color-white, #fff) 22%, transparent);
 }