feat(pwa): favicon, maskable icon, splash screens, runtime cache, safe-area insets

- Add favicon.ico, favicon-32x32.png, favicon-16x16.png
- Add dedicated maskable-512x512.png with safe-zone padding for Android adaptive icons
- Add iOS splash screens for 5 common device sizes (excluded from SW precache)
- Add NetworkFirst runtime caching for stable API routes (excludes volatile endpoints)
- Add safe-top inset to all view headers for PWA standalone mode
- Bump version to 0.2.2

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/SettingsView.tsx

@@ -55,7 +55,7 @@ export function SettingsView({ onBack }: { onBack: () => void }) {
   return (
     <div className="flex flex-col h-full bg-bg">
       {/* Header */}
-      <div className="flex items-center px-4 py-3 border-b border-border">
+      <div className="flex items-center px-4 py-3 border-b border-border safe-top">
         <button onClick={onBack} className="text-text-dim hover:text-text mr-2"><ChevronLeft className="w-5 h-5" /></button>
         <span className="text-lg font-medium text-text font-mono tracking-wide">Settings</span>
       </div>