feat: add MCP server with HTTP/SSE transport for AI integration

Exposes homelab topology to MCP-compatible AI clients (Claude Code, etc.)
over LAN via HTTP/SSE on port 8001.

- New mcp/ service: FastAPI + mcp SDK, SSE transport
- Auth: X-API-Key for AI clients, X-MCP-Service-Key for backend (Docker-internal)
- Resources: canvas, nodes, edges, scan/pending, scan/runs
- Tools: create/update/delete nodes+edges, trigger scan, approve/hide devices
- Backend deps.py: accepts JWT or MCP service key (no plain-text password)
- 40 tests (auth, resources, tools) across asyncio + trio
- docker-compose.yml: mcp service on port 8001
- README: MCP setup section with Claude Code/Desktop config examples

mcp/tests/conftest.py

@@ -0,0 +1,33 @@
+import os
+import pytest
+from unittest.mock import AsyncMock, patch
+from httpx import AsyncClient, ASGITransport
+
+os.environ.setdefault("MCP_API_KEY", "test_key")
+os.environ.setdefault("BACKEND_URL", "http://testbackend")
+os.environ.setdefault("AUTH_USERNAME", "admin")
+os.environ.setdefault("AUTH_PASSWORD", "admin")
+
+from app.main import app  # noqa: E402
+
+
+@pytest.fixture
+def api_key():
+    return "test_key"
+
+
+@pytest.fixture
+async def client(api_key):
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as c:
+        yield c
+
+
+@pytest.fixture
+def mock_backend():
+    with patch("app.resources.backend") as mock_res, \
+         patch("app.tools.backend") as mock_tools:
+        mock_res.get = AsyncMock()
+        mock_tools.post = AsyncMock()
+        mock_tools.patch = AsyncMock()
+        mock_tools.delete = AsyncMock()
+        yield {"resources": mock_res, "tools": mock_tools}