feat: initial Luma implementation

Full self-hosted photo manager with:
- Ingestion worker (chokidar + sharp + exifr, dHash perceptual hashing)
- SQLite schema with WAL mode (photos, tags, collections, duplicate_pairs)
- Express API with keyset pagination, tag/collection/search/date filters
- React + Vite UI: timeline, lightbox, detail panel, tag/collection editors
- Duplicate detection (Union-Find grouping) with review + dismiss UI
- Map view (Leaflet + OpenStreetMap, marker clustering)
- Docker multi-stage build + Compose with inline env config
- GitHub Actions: CI build check + ghcr.io image publish on main/tags

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/src/components/Timeline.jsx

@@ -0,0 +1,48 @@
+import MonthGroup from './MonthGroup.jsx';
+
+function groupByMonth(photos) {
+  const groups = [];
+  let current  = null;
+
+  for (const photo of photos) {
+    const key = photo.date_taken ? photo.date_taken.slice(0, 7) : 'undated';
+
+    if (!current || current.key !== key) {
+      current = { key, label: monthLabel(photo.date_taken), photos: [] };
+      groups.push(current);
+    }
+    current.photos.push(photo);
+  }
+
+  return groups;
+}
+
+function monthLabel(dateTaken) {
+  if (!dateTaken) return 'Undated';
+  return new Date(dateTaken).toLocaleDateString('en-US', { month: 'long', year: 'numeric' });
+}
+
+export default function Timeline({ photos, onSelect }) {
+  if (!photos.length) return null;
+
+  const groups = groupByMonth(photos);
+  let globalIdx = 0;
+
+  return (
+    <main style={{ padding: '0 3px' }}>
+      {groups.map(group => {
+        const startIdx = globalIdx;
+        globalIdx += group.photos.length;
+        return (
+          <MonthGroup
+            key={group.key}
+            label={group.label}
+            photos={group.photos}
+            startIdx={startIdx}
+            onSelect={onSelect}
+          />
+        );
+      })}
+    </main>
+  );
+}