feat(ui): add test notification preference and optimize Android TV logic

Introduce a "Test Notification" preference in the settings menu to allow users to verify the notification system. This preference is automatically hidden on Android TV devices to maintain a clean UI.

Additionally, refactor notification permission handling to skip requests on Android TV and improve the internal check for Leanback support using a lazy property.

Updated string resources for the new preference across all supported languages.

app/src/main/java/com/michatec/radio/MainActivity.kt

@@ -35,17 +35,16 @@ class MainActivity : AppCompatActivity() {
     /* Main class variables */
     private lateinit var appBarConfiguration: AppBarConfiguration
 
+    // Check if the device running the app is an Android TV instance
+    private val isAndroidTV: Boolean by lazy {
+        packageManager.hasSystemFeature(PackageManager.FEATURE_LEANBACK)
+    }
+
     // request notification permission (for Android 13+)
     private val permissionLauncher = registerForActivityResult(
         ActivityResultContracts.RequestPermission()
     ) { isGranted ->
-        if (isGranted) {
-            NotificationSys.showNotification(
-                this, 
-                R.string.app_name, 
-                R.string.notification_test_content
-            )
-        } else {
+        if (!isGranted) {
             Snackbar.make(
                 findViewById(android.R.id.content),
                 R.string.snackbar_failed_permission_notification, 
@@ -95,7 +94,7 @@ class MainActivity : AppCompatActivity() {
         supportActionBar?.hide()
 
         // TV-specific loading logic: Hide the overlay once the app is ready
-        if (packageManager.hasSystemFeature(PackageManager.FEATURE_LEANBACK)) {
+        if (isAndroidTV) {
             Handler(Looper.getMainLooper()).postDelayed({
                 hideLoadingOverlay()
             }, 1200)
@@ -107,14 +106,8 @@ class MainActivity : AppCompatActivity() {
         PreferencesHelper.registerPreferenceChangeListener(sharedPreferenceChangeListener)
 
         // request permissions
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+        if (!isAndroidTV && Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
             permissionLauncher.launch(Manifest.permission.POST_NOTIFICATIONS)
-        } else {
-            NotificationSys.showNotification(
-                this, 
-                R.string.app_name, 
-                R.string.notification_test_content
-            )
         }
     }
 

app/src/main/java/com/michatec/radio/SettingsFragment.kt

@@ -22,6 +22,8 @@ import com.michatec.radio.dialogs.PresetSelectionDialog
 import com.michatec.radio.dialogs.ThemeSelectionDialog
 import com.michatec.radio.dialogs.YesNoDialog
 import com.michatec.radio.helpers.*
+import com.michatec.radio.NotificationSys
+import android.content.pm.PackageManager
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers.IO
 import kotlinx.coroutines.launch
@@ -38,6 +40,11 @@ class SettingsFragment : PreferenceFragmentCompat(), YesNoDialog.YesNoDialogList
     /* Define log tag */
     private val TAG: String = SettingsFragment::class.java.simpleName
 
+    // Check if the device running the app is an Android TV instance
+    private val isAndroidTV: Boolean by lazy {
+        packageManager.hasSystemFeature(PackageManager.FEATURE_LEANBACK)
+    }
+
     /* Overrides onViewCreated from PreferenceFragmentCompat */
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
@@ -309,6 +316,21 @@ class SettingsFragment : PreferenceFragmentCompat(), YesNoDialog.YesNoDialogList
             return@setOnPreferenceClickListener true
         }
 
+        // set up "Test Notification" preference
+        val preferenceTestNotification = Preference(context)
+        preferenceTestNotification.title = getString(R.string.pref_test_notification_title)
+        preferenceTestNotification.setIcon(R.drawable.ic_notification_app_icon_white_24dp)
+        preferenceTestNotification.summary = getString(R.string.pref_test_notification_summary)
+        preferenceTestNotification.setOnPreferenceClickListener {
+            // show test notification
+            NotificationSys.showNotification(
+                context,
+                getString(R.string.pref_test_notification_title),
+                getString(R.string.notification_test_content)
+            )
+            return@setOnPreferenceClickListener true
+        }
+
         // set up "Security" preference
         val preferenceSecurity = Preference(context)
         preferenceSecurity.title = getString(R.string.pref_security_title)
@@ -364,6 +386,10 @@ class SettingsFragment : PreferenceFragmentCompat(), YesNoDialog.YesNoDialogList
         preferenceCategoryGeneral.addPreference(preferenceThemeSelection)
         preferenceCategoryGeneral.addPreference(preferenceLanguageSelection)
 
+        if (!isAndroidTV) {
+            preferenceCategoryGeneral.addPreference(preferenceTestNotification)
+        }
+
         screen.addPreference(preferenceCategoryAudioEffects)
         preferenceCategoryAudioEffects.addPreference(preferenceBassBoost)
         preferenceCategoryAudioEffects.addPreference(preferenceReverb)