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>

pyproject.toml

@@ -13,6 +13,7 @@ authors = [{ name = "Coulomb" }]
 dependencies = [
     "fastapi>=0.115,<1.0",
     "httpx>=0.27,<1.0",
+    "mcp>=1.9,<2.0",
     "PyYAML>=6.0,<7.0",
     "uvicorn[standard]>=0.30,<1.0",
 ]
@@ -20,6 +21,7 @@ dependencies = [
 [project.optional-dependencies]
 dev = [
     "pytest>=8.2,<9.0",
+    "pytest-asyncio>=0.24,<1.0",
     "ruff>=0.6,<1.0",
 ]
 
@@ -39,6 +41,7 @@ addopts = [
     "--disable-warnings",
     "--tb=short",
 ]
+asyncio_mode = "auto"
 
 [tool.ruff]
 line-length = 100