feat: web access via MCP (Firecrawl search/scrape) + mcp server attach support

- agent/web_mcp.py: stdio MCP server exposing web_search and web_scrape,
  backed by the self-hosted Firecrawl stack on xNAS (no API key needed)
- agent.py: Agent now attaches mcp_servers built from config; EXTRA_MCP_SERVERS
  env var allows adding arbitrary HTTP/SSE MCP servers as JSON
- Dockerfile: installs livekit-agents[mcp], copies web_mcp.py
- .env.example: WEB_MCP_ENABLED, FIRECRAWL_BASE, EXTRA_MCP_SERVERS documented

agent/pyproject.toml

@@ -10,6 +10,7 @@ requires-python = ">=3.10,<3.15"
 
 dependencies = [
     "livekit-agents~=1.7",
+    "livekit-agents[mcp]~=1.7",
     "livekit-plugins-azure~=1.7",
     "livekit-plugins-openai~=1.7",
     "python-dotenv",