test: add comprehensive AI feature install/uninstall test coverage

- Add 55 unit tests for feature-status.ts (installed.json CRUD, cache
  behavior, install lock, model verification, crash recovery, composite
  state) using real temp directories
- Add 36 integration tests for full install/uninstall lifecycle against
  Docker containers (face-detection bundle, SSE progress, tool gates,
  shared model protection, concurrent install prevention, auth guards,
  container restart recovery)
- Fix noise-removal CPU timeout by adding megapixel-based timeout
  calculation (120s/MP, min 5 minutes)
- Fix Playwright auth storage state race condition (mkdirSync before
  saving analytics-user.json)
- Fix 2 skipped tests in fixes-verification.spec.ts by replacing
  external ~/Downloads/sample dependency with existing test fixtures
- Enable skipped analytics-consent settings toggle test
- Restructure features.spec.ts to manage bundle state (uninstall/
  reinstall OCR) so 501 guard tests run instead of skipping
- Update noise-removal test mock to include sharp metadata() method

tests/unit/ai/noise-removal.test.ts

@@ -5,6 +5,7 @@ vi.mock("sharp", () => {
   const mockSharp = vi.fn(() => ({
     png: vi.fn().mockReturnThis(),
     toBuffer: vi.fn().mockResolvedValue(Buffer.from("mock-png-data")),
+    metadata: vi.fn().mockResolvedValue({ width: 800, height: 600 }),
   }));
   return { default: mockSharp };
 });
@@ -46,6 +47,7 @@ beforeEach(() => {
       ({
         png: vi.fn().mockReturnThis(),
         toBuffer: vi.fn().mockResolvedValue(Buffer.from("mock-png-data")),
+        metadata: vi.fn().mockResolvedValue({ width: 800, height: 600 }),
       }) as unknown as ReturnType<typeof sharp>,
   );
 });