FN-5724: fake-timer connectivity recovery app test

Stabilize the connectivity recovery first-run App test by controlling timer-driven state transitions.

- switch the retry/recovery test to `vi.useFakeTimers()` with `try/finally` cleanup
- advance timers explicitly around initial render, retry click, and post-rerender recovery window
- preserve existing assertions while removing `waitFor` timing dependence in this flow

Files changed:
 packages/dashboard/app/components/__tests__/App.test.tsx | 41 ++++++++++++++--------
 1 file changed, 26 insertions(+), 15 deletions(-)

Fusion-Task-Id: FN-5724
Fusion-Task-Lineage: 0dfad0d8-ccf9-4f83-af2e-1057180fe191

packages/dashboard/app/components/__tests__/App.test.tsx

@@ -876,6 +876,9 @@ describe("App backend-unreachable first-run flow", () => {
   });
 
   it("retries project loading and resumes setup wizard flow after connectivity recovers", async () => {
+    vi.useFakeTimers();
+
+    try {
       mockProjectsState.projects = [];
       mockProjectsState.error = "Backend unavailable";
       mockCurrentProjectState.currentProject = null;
@@ -886,21 +889,29 @@ describe("App backend-unreachable first-run flow", () => {
 
       const { rerender } = render(<App />);
 
-    await waitFor(() => {
+      await act(async () => {
+        await vi.advanceTimersByTimeAsync(1);
+      });
+
       expect(screen.getByRole("button", { name: "Retry Connection" })).toBeTruthy();
-    });
 
+      await act(async () => {
         fireEvent.click(screen.getByRole("button", { name: "Retry Connection" }));
-
+        await vi.advanceTimersByTimeAsync(1);
-    await waitFor(() => {
-      expect(mockRefreshProjects).toHaveBeenCalledTimes(1);
       });
 
+      expect(mockRefreshProjects).toHaveBeenCalledTimes(1);
+
       rerender(<App />);
 
-    await waitFor(() => {
+      await act(async () => {
+        await vi.advanceTimersByTimeAsync(1000);
+      });
+
       expect(screen.getByText("Welcome to Fusion")).toBeTruthy();
-    }, { timeout: 5000 });
+    } finally {
+      vi.useRealTimers();
+    }
   });
 });