Keep the system splash until the first real screen: no blank WebView gap, no second splash

Installed APK sequence was system splash -> white WebView -> web splash -> home. The
activity now holds the system splash (core-splashscreen) until the page calls
TadrisinoAndroid.appReady(), after its first non-boot screen; released after 10s or on a
main-frame load error so a dead site shows the WebView error, not an endless splash.
Older APKs have no appReady and are unaffected. Debug build compiles; not run on a device.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/lib/bazaar.ts

@@ -23,6 +23,8 @@ import { store } from './storage';
 interface AndroidBridge {
   bazaarPurchase?: (sku: string, orderId: string) => void;
   bazaarConsume?: (purchaseToken: string) => void;
+  /** اولین صفحه‌ی واقعی کشیده شد؛ اسپلشِ سیستم می‌تواند برود (APKهای قدیمی‌تر این را ندارند). */
+  appReady?: () => void;
 }
 
 declare global {