Remove local Puppeteer — Docker Chromium only

- Remove puppeteer dependency, use puppeteer-core instead (no bundled Chromium)
- Remove local launch fallback from browser-scraper
- Fail fast with clear error if CHROMIUM_WS is not set
- Simplify closeBrowser to disconnect only

Docker Chromium container is now required for JS-rendered stores.
Dev: docker compose -f docker-compose.dev.yml up -d
Prod: docker compose up (starts both app + chromium)

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

package.json

@@ -22,7 +22,7 @@
     "dotenv": "^16.4.7",
     "fastify": "^5.2.1",
     "p-limit": "^6.2.0",
-    "puppeteer": "^24.40.0",
+    "puppeteer-core": "^24.40.0",
     "puppeteer-extra": "^3.3.6",
     "puppeteer-extra-plugin-stealth": "^2.11.2",
     "sql.js": "^1.11.0",