Use remote Chromium container instead of local Puppeteer launch

- Add browserless/chromium container to docker-compose
- Add docker-compose.dev.yml for local dev (Chromium on port 3001)
- Browser scraper connects via WebSocket (CHROMIUM_WS env var)
- Falls back to local launch if CHROMIUM_WS not set
- Remove Chromium install from Dockerfile (smaller image)
- Auto-reconnect on browser disconnect

Tested: remote Chromium connects in ~500ms, HG Spot scrapes in
~2.2s total. No longer blocks the Node.js event loop.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -10,5 +10,15 @@ services:
       - NODE_ENV=production
       - DATABASE_PATH=/app/data/pricehunter.db
       - STORES_DIR=/app/stores
+      - CHROMIUM_WS=ws://chromium:3000
       - PORT=3000
+    depends_on:
+      - chromium
+    restart: unless-stopped
+
+  chromium:
+    image: ghcr.io/browserless/chromium
+    environment:
+      - MAX_CONCURRENT_SESSIONS=5
+      - CONNECTION_TIMEOUT=30000
     restart: unless-stopped