QONTO-WP-0003-T01: MCP adapter skeleton on shared capability core

Add a streamable-HTTP MCP adapter (mcp_server.py, official FastMCP SDK)
mounted at /mcp in the existing FastAPI app, with a combined lifespan so
the MCP session manager starts/stops with the service. Ships one smoke
tool (qonto_ping, no bank call) — real capability tools land in T02.

Prove REST and MCP hit the identical policy path: PolicyEngine.decide()
never branches on request.protocol, verified by a parametrized test.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_mcp_server.py

@@ -0,0 +1,25 @@
+import pytest
+
+from qonto_assistant.config import Settings
+from qonto_assistant.mcp_server import create_mcp_server
+
+
+def _settings() -> Settings:
+    settings = Settings.from_env()
+    return settings
+
+
+@pytest.mark.asyncio
+async def test_mcp_server_starts_and_lists_smoke_tool() -> None:
+    server = create_mcp_server(settings=_settings())
+    tools = await server.list_tools()
+    tool_names = {tool.name for tool in tools}
+    assert "qonto_ping" in tool_names
+
+
+@pytest.mark.asyncio
+async def test_mcp_server_smoke_tool_returns_no_bank_call() -> None:
+    server = create_mcp_server(settings=_settings())
+    result = await server.call_tool("qonto_ping", {})
+    payload = result[1] if isinstance(result, tuple) else result
+    assert payload is not None