Add app settings with update track and auto-check options

- Add AppSettingsScreen with update track selection and auto-check toggle
- Remove checkUpdateAvailable() as all vendors now support update checking
- Add missing Chinese translations for update-related strings

app/src/play/java/io/nekohasekai/sfa/vendor/Vendor.kt

@@ -12,14 +12,12 @@ import com.google.android.play.core.install.model.InstallStatus
 import com.google.android.play.core.install.model.UpdateAvailability
 import com.google.mlkit.common.MlKitException
 import io.nekohasekai.sfa.R
+import io.nekohasekai.sfa.update.UpdateInfo
+import io.nekohasekai.sfa.update.UpdateState
 
 object Vendor : VendorInterface {
     private const val TAG = "Vendor"
 
-    override fun checkUpdateAvailable(): Boolean {
-        return true
-    }
-
     override fun checkUpdate(
         activity: Activity,
         byUser: Boolean,
@@ -30,6 +28,7 @@ object Vendor : VendorInterface {
             when (appUpdateInfo.updateAvailability()) {
                 UpdateAvailability.UPDATE_NOT_AVAILABLE -> {
                     Log.d(TAG, "checkUpdate: not available")
+                    UpdateState.clear()
                     if (byUser) activity.showNoUpdatesDialog()
                 }
 
@@ -44,6 +43,7 @@ object Vendor : VendorInterface {
 
                 UpdateAvailability.UPDATE_AVAILABLE -> {
                     Log.d(TAG, "checkUpdate: available")
+                    UpdateState.hasUpdate.value = true
                     if (appUpdateInfo.isUpdateTypeAllowed(AppUpdateType.FLEXIBLE)) {
                         appUpdateManager.startUpdateFlow(
                             appUpdateInfo,
@@ -97,4 +97,15 @@ object Vendor : VendorInterface {
         // Per-app Proxy is disabled for Play Store builds due to QUERY_ALL_PACKAGES permission restriction
         return false
     }
+
+    override fun supportsTrackSelection(): Boolean {
+        // Play Store doesn't support track selection
+        return false
+    }
+
+    override fun checkUpdateAsync(): UpdateInfo? {
+        // Play Store updates are handled by the Play Core library
+        // We can't get version info in the same way as GitHub
+        return null
+    }
 }