feat(mcp): generic MCP tool source with per-node function filtering (#301)

* feat(mcp): generic MCP tool source with per-node function filtering

Adds a Model Context Protocol tool category: connect a customer MCP
server and expose its tools to the agent, with optional per-node
allow-listing of individual MCP functions.

- ToolCategory.MCP enum + alembic migration
- MCP definition validator and collision-safe function-name namespacing
- McpToolSession wrapper: graceful-degrade, per-call open/close lifecycle
- CustomToolManager MCP branch (schemas + proxy handlers)
- Per-node mcp_tool_filters threaded through DTO/graph/engine
- Best-effort discovered_tools catalog cache + POST /tools/{uuid}/mcp/refresh
- UI: MCP create/edit config, tabbed ToolSelector with per-node toggles

* feat: refactor for code standardisation and documentation

---------

Co-authored-by: Abhishek Kumar <abhishek@a6k.me>

scripts/setup_requirements.sh

@@ -51,7 +51,7 @@ fi
 
 # Install pipecat in editable mode with all extras
 echo "Installing pipecat dependencies..."
-pip install -e ./pipecat[cartesia,deepgram,openai,elevenlabs,groq,google,azure,sarvam,soundfile,silero,webrtc,speechmatics,openrouter,camb]
+pip install -e ./pipecat[cartesia,deepgram,openai,elevenlabs,groq,google,azure,sarvam,soundfile,silero,webrtc,speechmatics,openrouter,camb,mcp]
 
 if [ "$DEV_MODE" -eq 1 ]; then
     echo "Installing pipecat dev dependencies..."