Show service start failure details

Pass the optional failure message from the service layer through `MainServiceEvent` and show it in `MainViewModel` when available. This preserves the existing generic error toast as a fallback while surfacing more specific startup failures to the user.

V2rayNG/app/src/main/java/com/v2ray/ang/ui/main/MainRepository.kt

@@ -52,7 +52,9 @@ class MainRepository(
                 AppConfig.MSG_STATE_RUNNING -> MainServiceEvent.StateRunning
                 AppConfig.MSG_STATE_NOT_RUNNING -> MainServiceEvent.StateNotRunning
                 AppConfig.MSG_STATE_START_SUCCESS -> MainServiceEvent.StateStartSuccess
-                AppConfig.MSG_STATE_START_FAILURE -> MainServiceEvent.StateStartFailure
+                AppConfig.MSG_STATE_START_FAILURE -> MainServiceEvent.StateStartFailure(
+                    safeIntent.getStringExtra("content")
+                )
 
                 AppConfig.MSG_STATE_STOP_SUCCESS -> MainServiceEvent.StateStopSuccess
                 AppConfig.MSG_MEASURE_DELAY_RESULT -> safeIntent

V2rayNG/app/src/main/java/com/v2ray/ang/ui/main/MainServiceEvent.kt

@@ -7,7 +7,7 @@ sealed class MainServiceEvent {
     data object StateRunning : MainServiceEvent()
     data object StateNotRunning : MainServiceEvent()
     data object StateStartSuccess : MainServiceEvent()
-    data object StateStartFailure : MainServiceEvent()
+    data class StateStartFailure(val message: String? = null) : MainServiceEvent()
     data object StateStopSuccess : MainServiceEvent()
     data class MeasureDelayResult(val result: ConnectionTestResult, val requestId: String) : MainServiceEvent()
     data class MeasureDelayCancelled(val requestId: String) : MainServiceEvent()

V2rayNG/app/src/main/java/com/v2ray/ang/ui/main/MainViewModel.kt

@@ -134,8 +134,12 @@ class MainViewModel(
                 updateRunningState(true)
             }
 
-            MainServiceEvent.StateStartFailure -> {
+            is MainServiceEvent.StateStartFailure -> {
+                if (!event.message.isNullOrBlank()) {
+                    toastError(event.message)
+                } else {
                     toastError(R.string.toast_services_failure)
+                }
                 updateRunningState(false)
             }