fix: use correct Starlette mount pattern for MCP SSE routing

The previous implementation added health route directly to mcp_app and
returned it, which broke MCP's internal /mcp endpoint routing.

Now matches the working pattern from komodo-mcp-custom:
- Mount mcp_app at / inside a parent Starlette app
- Pass lifespan=mcp_app.lifespan for proper task group init
- Health check is a separate route in the parent app

src/monarch_mcp_custom/server.py

@@ -5,17 +5,13 @@ Monarch Money MCP Server - Custom SSE Implementation.
 import os
 import logging
 import json
-import asyncio
-from typing import Optional, List, Dict, Any
-from datetime import datetime
+from typing import Optional, Any
 
 from dotenv import load_dotenv
 from fastmcp import FastMCP
 from starlette.applications import Starlette
 from starlette.responses import JSONResponse
 from starlette.routing import Route, Mount
-from mcp.server.sse import SseServerTransport
-import uvicorn
 
 from monarch_mcp_custom.auth import get_authenticated_client
 
@@ -166,35 +162,36 @@ async def refresh_accounts() -> str:
         return f"Error: {str(e)}"
 
 
-# --- Health Check ---
+# --- Health Check Endpoint ---
 
 
-async def health_check(request):
-    """Simple health check endpoint."""
-    return JSONResponse({"status": "ok", "timestamp": datetime.now().isoformat()})
+async def health(request):
+    """Health check endpoint for Docker."""
+    return JSONResponse({"status": "ok"})
 
 
-# --- ASGI App Setup ---
+# --- ASGI Application ---
 
 
-def create_app() -> Starlette:
-    """Create the Starlette application with health check and MCP."""
+def create_app():
+    """Create the ASGI application with health check and MCP routes."""
     mcp_app = mcp.http_app()
 
-    # Add health check route directly to the MCP app
-    mcp_app.add_route("/health", health_check, methods=["GET"])
+    # Wrapper app: /health is standalone, everything else goes to MCP
+    # IMPORTANT: Must pass mcp_app.lifespan for task group initialization
+    routes = [
+        Route("/health", health, methods=["GET"]),
+        Mount("/", app=mcp_app),  # MCP handles /mcp endpoint
+    ]
 
-    return mcp_app
+    return Starlette(routes=routes, lifespan=mcp_app.lifespan)
 
 
+# Create the app instance for uvicorn
 app = create_app()
 
 
-def main():
-    """Entry point for running the server."""
-    port = int(os.getenv("PORT", 8000))
-    uvicorn.run(app, host="0.0.0.0", port=port)
-
-
 if __name__ == "__main__":
-    main()
+    import uvicorn
+
+    uvicorn.run(app, host="0.0.0.0", port=8000)