fix(frontend): pass isFetchingGraph prop to CodeGraph components

Add isFetchingGraph state to App.tsx and pass it to both desktop and
mobile CodeGraph components. Set true on fetch start, false in finally
block so the loading spinner renders correctly.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: gkorland

app/src/App.tsx

@@ -90,6 +90,7 @@ export default function App() {
   const [carouselApi, setCarouselApi] = useState<CarouselApi>()
   const [zoomedNodes, setZoomedNodes] = useState<Node[]>([])
   const [hasHiddenElements, setHasHiddenElements] = useState(false);
+  const [isFetchingGraph, setIsFetchingGraph] = useState(false);
 
   useEffect(() => {
     if (path?.start?.id && path?.end?.id) {
@@ -153,6 +154,7 @@ export default function App() {
   }
 
   async function onFetchGraph(graphName: string) {
+    setIsFetchingGraph(true);
     try {
       const result = await fetch(`/api/graph_entities?repo=${prepareArg(graphName)}`, {
         method: 'GET',
@@ -186,6 +188,8 @@ export default function App() {
         title: "Uh oh! Something went wrong.",
         description: "Failed to load repository graph. Please try again.",
       })
+    } finally {
+      setIsFetchingGraph(false);
     }
   }
 
@@ -527,6 +531,7 @@ export default function App() {
                   options={options}
                   setOptions={setOptions}
                   onFetchGraph={onFetchGraph}
+                  isFetchingGraph={isFetchingGraph}
                   onFetchNode={onFetchNode}
                   setPath={setPath}
                   isShowPath={!!path}
@@ -654,6 +659,7 @@ export default function App() {
                 options={options}
                 setOptions={setOptions}
                 onFetchGraph={onFetchGraph}
+                isFetchingGraph={isFetchingGraph}
                 onFetchNode={onFetchNode}
                 setPath={setPath}
                 isShowPath={!!path}