feat: add docker-compose.dev.yml for dev mode with hot reload

Run with: docker compose -f docker-compose.dev.yml up
Mounts source code, runs npm run dev, shows DevToolbar.

docker-compose.dev.yml

@@ -0,0 +1,17 @@
+# Dev mode: hot reload, source mounted, DevToolbar visible
+services:
+  lightbox:
+    image: node:20-alpine
+    container_name: immich-folio-dev
+    working_dir: /app
+    command: sh -c "npm install && npm run dev -- --hostname 0.0.0.0 --port 7211"
+    ports:
+      - '7211:7211'
+    env_file:
+      - .env.local
+    environment:
+      - NODE_ENV=development
+    volumes:
+      - .:/app
+      - /app/node_modules # anonymous volume to avoid overwriting container's node_modules
+      - ./content:/app/content