Playwright con Chromium + fetch con uvx + executable-path fix

- Dockerfile: instalar deps sistema Playwright (root) + Chromium (appuser)
- Dockerfile: instalar uv/uvx para mcp-server-fetch
- mcp.json: --executable-path apunta al Chromium instalado por appuser
- Eliminar entrypoint (dnsmasq resuelve DNS dinámicamente)

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

mcp.json

@@ -9,7 +9,7 @@
     },
     "playwright": {
       "command": "npx",
-      "args": ["@playwright/mcp", "--headless"],
+      "args": ["@playwright/mcp", "--headless", "--executable-path", "/home/appuser/.cache/ms-playwright/chromium-1212/chrome-linux64/chrome"],
       "timeout": 30,
       "startup_timeout": 15
     },