feat: show clear error when p12 certificate import fails

The import previously swallowed all exceptions silently. Now the upload
config dialog shows a specific message for: wrong password, expired
certificate, invalid file, and unknown failures.

feature/settings/src/main/java/com/rtbishop/look4sat/feature/settings/LoTWUploadConfigDialog.kt

@@ -78,6 +78,7 @@ fun LoTWUploadConfigDialog(
     certificate: LoTWCertificate?,
     station: LoTWStation?,
     busy: Boolean,
+    error: LoTWUploadError?,
     onDismiss: () -> Unit,
     onImport: (ByteArray, CharArray) -> Unit,
     onRemove: () -> Unit,
@@ -122,6 +123,20 @@ fun LoTWUploadConfigDialog(
                 isEnabled = !busy,
                 modifier = Modifier.fillMaxWidth()
             )
+            error?.let {
+                Text(
+                    text = stringResource(
+                        when (it) {
+                            LoTWUploadError.PASSWORD -> R.string.prefs_lotw_upload_error_password
+                            LoTWUploadError.EXPIRED -> R.string.prefs_lotw_upload_error_expired
+                            LoTWUploadError.INVALID_FILE -> R.string.prefs_lotw_upload_error_invalid
+                            LoTWUploadError.UNKNOWN -> R.string.prefs_lotw_upload_error_unknown
+                        }
+                    ),
+                    color = MaterialTheme.colorScheme.error,
+                    fontSize = 12.sp
+                )
+            }
             selectedFile?.let { uri ->
                 Text(
                     text = displayName(uri),

feature/settings/src/main/java/com/rtbishop/look4sat/feature/settings/SettingsScreen.kt

@@ -273,6 +273,7 @@ private fun SettingsScreen(uiState: SettingsState, onAction: (SettingsAction) ->
             certificate = uiState.lotwCertificate,
             station = uiState.lotwStation,
             busy = uiState.lotwUploadBusy,
+            error = uiState.lotwUploadError,
             onDismiss = { dialogs.lotwUpload = false },
             onImport = { bytes, password -> onAction(SettingsAction.ImportLoTWCertificate(bytes, password)) },
             onRemove = { onAction(SettingsAction.RemoveLoTWCertificate) },

feature/settings/src/main/java/com/rtbishop/look4sat/feature/settings/SettingsState.kt

@@ -75,6 +75,8 @@ data class SettingsState(
     /** LoTW upload station location (null when unset). */
     val lotwStation: com.rtbishop.look4sat.core.domain.repository.LoTWStation? = null,
     val lotwUploadBusy: Boolean = false,
+    /** Last certificate import outcome; shown inside the upload config dialog. */
+    val lotwUploadError: LoTWUploadError? = null,
     /** 指南针校准精度等级 (校准对话框进度条). */
     val compassAccuracy: CompassAccuracy = CompassAccuracy.UNRELIABLE,
     /** 校正后航向(度, 含磁偏角+手动偏置), 校准对话框实时显示. */
@@ -91,6 +93,8 @@ sealed interface LoTWError {
     data class Network(val detail: String) : LoTWError
 }
 
+enum class LoTWUploadError { PASSWORD, INVALID_FILE, EXPIRED, UNKNOWN }
+
 sealed interface SettingsAction {
     // Position
     data object SetGpsPosition : SettingsAction

feature/settings/src/main/java/com/rtbishop/look4sat/feature/settings/SettingsViewModel.kt

@@ -354,12 +354,19 @@ class SettingsViewModel(
 
     private fun importLoTWCertificate(bytes: ByteArray, password: CharArray) {
         viewModelScope.launch {
-            _uiState.update { it.copy(lotwUploadBusy = true) }
+            _uiState.update { it.copy(lotwUploadBusy = true, lotwUploadError = null) }
             try {
                 val cert = lotwUploadRepository.importCertificate(bytes, password)
-                _uiState.update { it.copy(lotwCertificate = cert, lotwUploadBusy = false) }
+                _uiState.update { it.copy(lotwCertificate = cert, lotwUploadBusy = false, lotwUploadError = null) }
+            } catch (e: com.rtbishop.look4sat.core.domain.repository.LoTWOperationException) {
+                val error = when (e.reason) {
+                    com.rtbishop.look4sat.core.domain.repository.LoTWProblem.CERTIFICATE_PASSWORD -> LoTWUploadError.PASSWORD
+                    com.rtbishop.look4sat.core.domain.repository.LoTWProblem.CERTIFICATE_EXPIRED -> LoTWUploadError.EXPIRED
+                    else -> LoTWUploadError.INVALID_FILE
+                }
+                _uiState.update { it.copy(lotwUploadBusy = false, lotwUploadError = error) }
             } catch (_: Exception) {
-                _uiState.update { it.copy(lotwUploadBusy = false) }
+                _uiState.update { it.copy(lotwUploadBusy = false, lotwUploadError = LoTWUploadError.UNKNOWN) }
             }
         }
     }