feat: ship as a real iOS-installable PWA, restructure bottom nav, fix safe-area

- Add manifest.webmanifest with standalone display + warm-craft theme colors,
  apple-touch-icon, and 192/512/512-maskable icons (frame-with-sunset glyph).
- Add PWA meta tags + viewport-fit=cover so add-to-home-screen produces a
  true standalone app on iOS instead of a Safari bookmark.
- Drop the Shared bottom-nav tab; the in-page sub-tabs already cover that.
  Three nav tabs total (Home / Library / Settings); pending-share badge
  moves to the Library tab. Predicate-based isActive() now correctly
  disambiguates /library vs /library?tab=shared.
- Safe-area handling: bottom nav, bottom sheet, upload overlay, and #app
  respect env(safe-area-inset-*); sticky Library tabs anchor below the
  iPhone status bar. Introduces --bottom-nav-height token consumed by
  Settings, Library, and the toast.
- LibraryView reactively follows route.query.tab so deep-linking
  /library?tab=shared lands on the right sub-tab.
- Theme-color meta syncs client-side via useTheme.applyTheme so the
  user's chosen theme follows them into Android Chrome's chrome bar.

Test suite expanded to 278 tests / 100% line coverage (99.84% statements,
99.78% branches). Remaining gaps are unreachable defensive code.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/vite.config.ts

@@ -21,11 +21,15 @@ export default defineConfig({
     coverage: {
       provider: 'v8',
       reporter: ['text', 'html'],
+      include: ['src/**/*.{ts,vue}'],
       exclude: [
         'src/components/CropEditor.vue',
         'src/components/StickerCanvas.vue',
         'src/assets/**',
         'src/test/**',
+        'src/types/**',
+        'src/main.ts',
+        'src/router/**',
       ]
     }
   }