Initial implementation of duplicate finder

Full project per spec: FastAPI backend, 4-method duplicate detection
(SHA-256, phash, EXIF, filesize), Google Takeout pre-processor,
4 scan modes, and dark-theme vanilla JS gallery frontend.

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

docker-compose.yml

@@ -0,0 +1,17 @@
+services:
+  dup-finder:
+    build: .
+    container_name: dup-finder
+    restart: unless-stopped
+    ports:
+      - "8765:8000"
+    volumes:
+      # Mount the photo library — READ ONLY, never modified
+      - /volume1/photos:/photos:ro
+      # Database persistence
+      - /volume1/docker/dup-finder/data:/data
+    deploy:
+      resources:
+        limits:
+          cpus: "2.0"
+          memory: 2G