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>

src/server/config.ts

@@ -5,5 +5,6 @@ export const config = {
   host: process.env.HOST || '0.0.0.0',
   databasePath: process.env.DATABASE_PATH || './data/pricehunter.db',
   storesDir: process.env.STORES_DIR || './stores',
+  chromiumWs: process.env.CHROMIUM_WS || '',
   isProduction: process.env.NODE_ENV === 'production',
 };