Add Foundry mobile layout with Tauri iOS/Android support

- Add responsive mobile layout with bottom pill tab bar, swipe navigation, and task list as home screen
- Add platform detection (useIsMobile hook) with viewport breakpoint and VITE_MOBILE build flag
- Mobile-optimize settings/billing/account pages (single-column layout with horizontal tabs)
- Add iOS safe area inset handling with 47px minimum padding
- Scaffold Tauri v2 mobile targets (iOS/Android) with platform-gated sidecar and capabilities
- Add notification sound support and mobile build script

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

foundry/packages/desktop/package.json

@@ -5,10 +5,16 @@
   "type": "module",
   "scripts": {
     "dev": "tauri dev",
+    "dev:ios": "VITE_MOBILE=1 tauri ios dev",
+    "dev:android": "VITE_MOBILE=1 tauri android dev",
     "build": "tauri build",
+    "build:ios": "tauri ios build",
+    "build:android": "tauri android build",
     "build:sidecar": "tsx scripts/build-sidecar.ts",
     "build:frontend": "tsx scripts/build-frontend.ts",
+    "build:frontend:mobile": "tsx scripts/build-frontend-mobile.ts",
     "build:all": "pnpm build:sidecar && pnpm build:frontend && pnpm build",
+    "build:all:ios": "pnpm build:frontend:mobile && pnpm build:ios",
     "tauri": "tauri"
   },
   "devDependencies": {