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/app/backend_client.py

@@ -0,0 +1,40 @@
+import httpx
+from .config import settings
+
+
+class BackendClient:
+    def __init__(self):
+        self._client: httpx.AsyncClient | None = None
+
+    async def start(self):
+        self._client = httpx.AsyncClient(
+            base_url=settings.backend_url,
+            headers={"X-MCP-Service-Key": settings.mcp_service_key},
+            timeout=30.0,
+        )
+
+    async def stop(self):
+        if self._client:
+            await self._client.aclose()
+
+    async def request(self, method: str, path: str, **kwargs) -> dict:
+        resp = await self._client.request(method, path, **kwargs)
+        resp.raise_for_status()
+        if resp.status_code == 204:
+            return {}
+        return resp.json()
+
+    async def get(self, path: str) -> dict | list:
+        return await self.request("GET", path)
+
+    async def post(self, path: str, body: dict) -> dict:
+        return await self.request("POST", path, json=body)
+
+    async def patch(self, path: str, body: dict) -> dict:
+        return await self.request("PATCH", path, json=body)
+
+    async def delete(self, path: str) -> dict:
+        return await self.request("DELETE", path)
+
+
+backend = BackendClient()