refactor: mount FastMCP app at root and retain /health for compatibility

src/monarch_mcp_custom/server.py

@@ -184,12 +184,13 @@ def create_app():
     # FastMCP.http_app() already includes its own health check and SSE routes.
     # By default it uses /sse for the stream and /messages for POSTs.
 
-    routes = [
-        Route("/health", health_check, methods=["GET"]),
-        Mount("/mcp", app=mcp_app),
-    ]
-
-    return Starlette(routes=routes, lifespan=mcp_app.lifespan)
+    return Starlette(
+        routes=[
+            Route("/health", health_check, methods=["GET"]),
+            Mount("/", app=mcp_app),
+        ],
+        lifespan=mcp_app.lifespan,
+    )
 
 
 app = create_app()