Use a reverse-domain redirect scheme for the native app

- Android/iOS now return to cat.ikerdemo.musify:/callback instead of
  musify://callback: a private-use scheme based on a domain we own
  (RFC 8252 section 7.1), so another app is unlikely to claim it.
- The Musify Native app no longer needs devMode: loopback and custom
  scheme redirects are both valid for a native app.
- zitadel-init also updates an existing app's config, so the change
  reaches instances created before it (the client id is kept).
- iOS takes the scheme from everything before the first ':', since the
  new URI has a single slash.

mobile/README.md

@@ -54,7 +54,7 @@ al patrón que ya usa Scalar para probar la API — ver `deploy/compose.yml` (`z
 
 Redirect URIs registrados:
 - Desktop: `http://127.0.0.1:17453/callback` (RFC 8252, loopback con puerto fijo).
-- Android / iOS: `musify://callback` (custom scheme).
+- Android / iOS: `cat.ikerdemo.musify:/callback` (custom scheme con dominio invertido, RFC 8252 §7.1).
 
 `mobile/gradle.properties` controla a qué backend apunta Android/Desktop:
 
@@ -125,13 +125,13 @@ Kotlin/Native (`iosMain/`) sigue las APIs estándar de interop (`AVFoundation`,
 
 1. Genera un proyecto Xcode con el asistente "Kotlin Multiplatform" de Android Studio, o crea uno vacío
    e importa `composeApp` como framework (`./gradlew :composeApp:embedAndSignAppleFrameworkForXcode`).
-2. Registra el scheme `musify` en `Info.plist`:
+2. Registra el scheme `cat.ikerdemo.musify` en `Info.plist`:
    ```xml
    <key>CFBundleURLTypes</key>
    <array>
      <dict>
        <key>CFBundleURLSchemes</key>
-       <array><string>musify</string></array>
+       <array><string>cat.ikerdemo.musify</string></array>
      </dict>
    </array>
    ```

mobile/composeApp/src/androidMain/AndroidManifest.xml

@@ -18,7 +18,9 @@
             </intent-filter>
         </activity>
 
-        <!-- Catches the `musify://callback` redirect Zitadel sends after login/register.
+        <!-- Catches the `cat.ikerdemo.musify:/callback` redirect Zitadel sends after
+             login/register. The URI has no host, so the filter matches on the scheme
+             alone.
              See BrowserAuthLauncher.android.kt and AppConfig.nativeRedirectUri. -->
         <activity
             android:name=".auth.AuthCallbackActivity"
@@ -29,7 +31,7 @@
                 <action android:name="android.intent.action.VIEW" />
                 <category android:name="android.intent.category.DEFAULT" />
                 <category android:name="android.intent.category.BROWSABLE" />
-                <data android:scheme="musify" android:host="callback" />
+                <data android:scheme="cat.ikerdemo.musify" />
             </intent-filter>
         </activity>
     </application>

mobile/composeApp/src/androidMain/kotlin/com/musify/app/Config.android.kt

@@ -9,5 +9,5 @@ actual object AppConfig {
 
     // Matches the AuthCallbackActivity intent-filter in AndroidManifest.xml and
     // the redirect URI registered for the "Musify Native" app in Zitadel.
-    actual val nativeRedirectUri: String = "musify://callback"
+    actual val nativeRedirectUri: String = "cat.ikerdemo.musify:/callback"
 }

mobile/composeApp/src/androidMain/kotlin/com/musify/app/auth/AuthCallbackActivity.kt

@@ -5,7 +5,7 @@ import android.content.Intent
 import android.os.Bundle
 
 /**
- * Declared in AndroidManifest.xml with an intent-filter for `musify://callback`.
+ * Declared in AndroidManifest.xml with an intent-filter for `cat.ikerdemo.musify:/callback`.
  * Chrome Custom Tabs redirects here once Zitadel finishes the login/register
  * flow; this activity just forwards the URL to [AndroidAuthBridge] and closes.
  */

mobile/composeApp/src/commonMain/kotlin/com/musify/app/Config.kt

@@ -9,7 +9,8 @@ package com.musify.app
  * `nativeRedirectUri` is the OAuth redirect registered for the "Musify
  * Native" Zitadel app (see deploy/compose.yml, zitadel-init): a fixed
  * loopback port on Desktop (RFC 8252 native-app loopback flow), and the
- * `musify://callback` custom scheme on Android/iOS.
+ * `cat.ikerdemo.musify:/callback` reverse-domain custom scheme on Android/iOS
+ * (RFC 8252 §7.1: based on a domain we own, so no other app plausibly claims it).
  */
 expect object AppConfig {
     val apiBaseUrl: String

mobile/composeApp/src/commonMain/kotlin/com/musify/app/auth/BrowserAuthLauncher.kt

@@ -12,7 +12,7 @@ package com.musify.app.auth
  *  - Desktop: a one-shot loopback HTTP server on the fixed port registered in
  *    Zitadel (RFC 8252 §7.3), opened via the OS default browser.
  *  - Android: Chrome Custom Tabs; the redirect is caught by
- *    [AuthCallbackActivity] via the `musify://callback` intent filter.
+ *    [AuthCallbackActivity] via the `cat.ikerdemo.musify:/callback` intent filter.
  *  - iOS: `ASWebAuthenticationSession`, which owns the whole round trip.
  */
 expect class BrowserAuthLauncher() {

mobile/composeApp/src/iosMain/kotlin/com/musify/app/Config.ios.kt

@@ -12,5 +12,5 @@ actual object AppConfig {
 
     // Matches CFBundleURLTypes in Info.plist and the redirect URI registered
     // for the "Musify Native" app in Zitadel.
-    actual val nativeRedirectUri: String = "musify://callback"
+    actual val nativeRedirectUri: String = "cat.ikerdemo.musify:/callback"
 }

mobile/composeApp/src/iosMain/kotlin/com/musify/app/auth/BrowserAuthLauncher.ios.kt

@@ -23,14 +23,15 @@ private class PresentationContextProvider : NSObject(), ASWebAuthenticationPrese
 /**
  * `ASWebAuthenticationSession` owns the whole round trip: it opens a system
  * browser sheet at [authorizeUrl] (Zitadel's hosted login, with its
- * "Regístrate" link) and intercepts the `musify://` redirect itself, no app
+ * "Regístrate" link) and intercepts the `cat.ikerdemo.musify:` redirect itself, no app
  * delegate / `onOpenURL` wiring required.
  */
 @OptIn(ExperimentalForeignApi::class)
 actual class BrowserAuthLauncher actual constructor() {
     actual suspend fun launch(authorizeUrl: String, redirectUri: String): String =
         suspendCancellableCoroutine { continuation ->
-            val scheme = redirectUri.substringBefore("://")
+            // `scheme:/path` (RFC 8252 private-use scheme): everything before the first ':'.
+            val scheme = redirectUri.substringBefore(":")
             val contextProvider = PresentationContextProvider()
 
             val session = ASWebAuthenticationSession(