Bazaar: subscriptions (subscribeProduct), dynamic price token, RSA key; Zarinpal and Bazaar side by side at checkout

- Checkout sheet always shows both methods as two tiles; Bazaar tile disabled with the reason
  (not in Bazaar / Android app only / update the app) instead of hidden; default is Bazaar inside an app that can buy.
- Bridge v2: TadrisinoAndroid.bazaarBuy(sku, orderId, productType, dynamicPriceToken); inAndroidApp() split
  from canBuyFromBazaar() so the pay.html workaround still applies to the installed APK.
- Bazaar flow: order -> optional discount code -> POST /payment/bazaar/orders/{id}/start -> Poolakey -> verify;
  consume only packs.
- Android: RSA key, subscribeProduct/getSubscribedProducts for subscriptions, dynamicPriceToken, versionCode 2.
  compileDebugKotlin green; no purchase tested on a phone.

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

android/app/build.gradle.kts

@@ -64,13 +64,15 @@ android {
         applicationId = "com.tadrisino.math.app"
         minSdk = 23
         targetSdk = 34
-        versionCode = 1
-        versionName = "1.0.0"
+        // بازار نسخه‌ی تازه را فقط با versionCodeِ بزرگ‌تر می‌پذیرد؛ هر build که منتشر می‌شود یکی بالا.
+        versionCode = 2
+        versionName = "1.1.0"
 
         // URL of the web frontend.
         buildConfigField("String", "WEB_URL", "\"https://math.tadrisino2.ir/\"")
-        // Public RSA key from the Cafe Bazaar panel. Purchases won't start until it is filled in.
-        buildConfigField("String", "BAZAAR_RSA_KEY", "\"\"")
+        // کلیدِ RSAِ عمومیِ اپ از پیشخانِ بازار (پرداخت درون‌برنامه‌ای)؛ سینیور، ۲۰۲۶-۱۰-۱۲. عمومی است و در APK
+        // می‌رود؛ Poolakey با آن امضای خرید را روی گوشی می‌سنجد. سنجشِ اصلی سمتِ سرور است.
+        buildConfigField("String", "BAZAAR_RSA_KEY", "\"MIHNMA0GCSqGSIb3DQEBAQUAA4G7ADCBtwKBrwC9EBw0RW6jeTdHkrJwfB/mX+klpjpVXVb2stpGDcixeqHiLE+/Iow+PiMbZEQfxZDuED6ELvZlzQX+ALOlGRPxaa1ctl6/Uy6wGaPXhGPDpZL6jPrXV88mjJzMcEoB4sf3yNb+6YNKrvKhRyXXR0JdMUmPMqMe8igmQZTv/UF+QEMNqv7lg7qw9Yl+fG802nqjasft7qUPQK+YHJYPS4PJ5Pj/YpTkGDdDmVi7AIMCAwEAAQ==\"")
     }
 
     buildFeatures {