test(web+mobile): Playwright E2E scaffold + 23 mobile store tests [C4, B7]
- web: playwright.config.ts + e2e/navigation.spec.ts (7 navigation tests, scaffolded)
- web: exclude e2e/ from tsconfig (playwright not yet installed as dep)
- mobile: notes-store.test.ts (7 tests: hydrate, openNote, saveDraft, updateNote)
- mobile: workspace-store.test.ts (5 tests: hydrate, preserve/reset active, set/clear)
- mobile: inbox-store.test.ts (5 tests: hydrate, approve, reject, unknown id guards)
- mobile: auth-store.test.ts (6 tests: bootstrap, signIn, signOut, failure paths)
- Total: 76 backend, 14 web, 23 mobile = 113 tests