fix: PWA improvements — clean up SW, fix chin bar, add shortcuts, improve mobile support

- Remove dead precache manifest from SW (no fetch handler to consume it)
- Set empty globPatterns in vite-plugin-pwa config
- Fix bottom chin bar padding: use scaled safe-area token instead of raw inset
- Add 'New Session' PWA shortcut (client + server manifest)
- Add PWA meta tags to mobile.html (manifest, Apple icons, theme-color)
- Fix static site.webmanifest: add id/scope, correct description
- Remove duplicate apple-mobile-web-app-title from index.html
- Move SW registration to module scope (earlier, no window.load delay)
- Update manifest route tests for new shortcut order

packages/ui/src/styles/mobile.css

@@ -716,7 +716,7 @@
   }
 
   :root:not(.oc-capacitor-app):not(.oc-browser-keyboard-open) .oc-mobile-composer {
-    padding-bottom: calc(0.75rem + max(16px, var(--oc-safe-area-bottom, env(safe-area-inset-bottom, 0px)))) !important;
+    padding-bottom: calc(0.75rem + var(--oc-safe-area-bottom-visual, 0px)) !important;
   }
 
   /* Fullscreen composer: ChatInput pins the form to the visual viewport from