feat: add iOS Safari install guide and improve PWA UX with neutral theme

- Add iOS Safari install prompt with step-by-step modal guide
- Fix Telegram environment detection (check initData, not just SDK presence)
- Fix install prompt re-entrancy issue (clear deferredPrompt immediately)
- Extract icon components to separate file (web/src/components/icons.tsx)
- Rename "Happy App" to "Hapi" throughout the UI and manifests
- Change button/icon colors from blue (--app-button) to neutral theme (--app-fg/--app-bg)
- Add install dismiss state to prevent repeated prompts
- Improve iOS Safari detection with robust user agent parsing

web/src/hooks/usePlatform.ts

@@ -68,8 +68,14 @@ function createHaptic(): PlatformHaptic {
 // Singleton haptic instance (functions are stable)
 const haptic = createHaptic()
 
+function checkIsTelegram(): boolean {
+    const tg = getTelegramWebApp()
+    // SDK is always loaded, but initData is only present in actual Telegram environment
+    return tg !== null && Boolean(tg.initData)
+}
+
 export function usePlatform(): Platform {
-    const isTelegram = useMemo(() => getTelegramWebApp() !== null, [])
+    const isTelegram = useMemo(() => checkIsTelegram(), [])
 
     return {
         isTelegram,
@@ -80,7 +86,7 @@ export function usePlatform(): Platform {
 // Non-hook version for use outside React components
 export function getPlatform(): Platform {
     return {
-        isTelegram: getTelegramWebApp() !== null,
+        isTelegram: checkIsTelegram(),
         haptic
     }
 }