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>

.env.example

@@ -0,0 +1,9 @@
+# Path to your photo library (read-only mount in production)
+PHOTO_DIR=./photos
+
+# Where the SQLite DB and generated posters live (writable volume)
+DB_PATH=./data/library.db
+POSTER_DIR=./data/posters
+
+# API server port
+PORT=3000