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/MonthGroup.jsx

@@ -0,0 +1,36 @@
+import PhotoCard from './PhotoCard.jsx';
+
+export default function MonthGroup({ label, photos, startIdx, onSelect }) {
+  return (
+    <section style={{ marginBottom: 8 }}>
+      <h2 style={{
+        padding: '18px 6px 8px',
+        fontSize: 13,
+        fontWeight: 600,
+        color: '#666',
+        letterSpacing: 0.4,
+        textTransform: 'uppercase',
+        userSelect: 'none',
+      }}>
+        {label}
+        <span style={{ marginLeft: 8, color: '#3a3a3a', fontWeight: 400 }}>
+          {photos.length.toLocaleString()}
+        </span>
+      </h2>
+
+      <div style={{
+        display: 'grid',
+        gridTemplateColumns: 'repeat(auto-fill, minmax(160px, 1fr))',
+        gap: 3,
+      }}>
+        {photos.map((photo, i) => (
+          <PhotoCard
+            key={photo.id}
+            photo={photo}
+            onClick={() => onSelect(startIdx + i)}
+          />
+        ))}
+      </div>
+    </section>
+  );
+}