test(frontend): add component tests — TimeEntryForm, WeeklyView, App smoke

- TimeEntryForm.test.tsx: fills date/project/h:mm, clicks submit,
  asserts fetch called with correct JSON body (mocked fetch)
- WeeklyView.test.tsx: renders with stubbed WeeklyReport fixture,
  asserts each day's h:mm and the week total display correctly
- App.test.tsx: smoke test — renders layout with TopBar and main content

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/tests/App.test.tsx

@@ -1,10 +1,31 @@
 import { render, screen } from "@testing-library/react";
-import { describe, expect, it } from "vitest";
+import { MemoryRouter } from "react-router-dom";
+import { describe, expect, it, vi } from "vitest";
 import App from "../src/App";
 
+// minimal stub so App renders without network calls
+vi.mock("../src/lib/api", () => ({
+  api: {
+    users: { list: vi.fn().mockResolvedValue([]) },
+    reports: {
+      weekly: vi.fn().mockResolvedValue({
+        days: [],
+        weekTotalMinutes: 0,
+        weekTotalCostCents: 0,
+      }),
+    },
+    timeEntries: { list: vi.fn().mockResolvedValue([]) },
+  },
+}));
+
 describe("App", () => {
-  it("renders a main element", () => {
-    render(<App />);
+  it("renders the top bar and main content area", () => {
+    render(
+      <MemoryRouter initialEntries={["/weekly"]}>
+        <App />
+      </MemoryRouter>,
+    );
+    expect(screen.getByText("TimeTracker")).toBeDefined();
     expect(screen.getByRole("main")).toBeDefined();
   });
 });