feat: USB dashcam file browser on Dashcam tab

- PiApi extended: listDashcamFiles, deleteDashcamFile, importDashcamFiles
- DTO: DashcamFilesResponse, DashcamDevice, DashcamFile
- DashcamScreen: USB Dashcam card with status, file count, Import All + Refresh
- ViewModel: loadDashcamFiles, deleteDashcamFile, importDashcamFiles

android/app/src/main/java/com/yarisobd/app/DashcamScreen.kt

@@ -12,6 +12,7 @@ import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.items
@@ -40,6 +41,7 @@ import androidx.compose.ui.unit.dp
 import coil3.compose.AsyncImage
 import coil3.request.ImageRequest
 import coil3.request.crossfade
+import com.yarisobd.app.data.remote.dto.DashcamFile
 import com.yarisobd.app.data.remote.dto.VideoFile
 
 @Composable
@@ -50,13 +52,46 @@ fun DashcamScreen(
     isLoading: Boolean,
     error: String?,
     downloadProgress: Map<String, DownloadProgress>,
+    dashcamFiles: List<DashcamFile>,
+    dashcamTotalSize: Long,
+    dashcamStatus: String,
+    dashcamLoading: Boolean,
     onRefresh: () -> Unit,
     onDownload: (VideoFile) -> Unit,
     onDelete: (VideoFile) -> Unit,
+    onDeleteDashcam: (DashcamFile) -> Unit,
+    onImport: (List<String>?) -> Unit,
 ) {
     Column(modifier = Modifier.fillMaxSize()) {
         com.yarisobd.app.ui.components.YarisHeader()
 
+        // USB Dashcam section
+        Card(
+            modifier = Modifier.fillMaxWidth().padding(horizontal = 16.dp, vertical = 4.dp),
+            colors = CardDefaults.cardColors(containerColor = MaterialTheme.colorScheme.surfaceContainerHigh)
+        ) {
+            Column(modifier = Modifier.padding(12.dp)) {
+                Text("USB Dashcam", style = MaterialTheme.typography.titleSmall, color = MaterialTheme.colorScheme.primary)
+                when (dashcamStatus) {
+                    "ok" -> {
+                        Text("${dashcamFiles.size} files · ${formatBytes(dashcamTotalSize)}", style = MaterialTheme.typography.bodySmall, color = MaterialTheme.colorScheme.onSurfaceVariant)
+                        if (dashcamFiles.isNotEmpty()) {
+                            Spacer(Modifier.height(4.dp))
+                            Row {
+                                Button(onClick = { onImport(null) }, modifier = Modifier.weight(1f), contentPadding = PaddingValues(horizontal = 8.dp, vertical = 4.dp)) { Text("Import All", style = MaterialTheme.typography.bodySmall) }
+                                Spacer(Modifier.width(4.dp))
+                                Button(onClick = onRefresh, enabled = !dashcamLoading, modifier = Modifier.weight(1f), colors = ButtonDefaults.buttonColors(containerColor = MaterialTheme.colorScheme.secondary), contentPadding = PaddingValues(horizontal = 8.dp, vertical = 4.dp)) { Text(if (dashcamLoading) "..." else "Refresh", style = MaterialTheme.typography.bodySmall) }
+                            }
+                        }
+                    }
+                    "no_device" -> Text("No USB dashcam connected", style = MaterialTheme.typography.bodySmall, color = MaterialTheme.colorScheme.error)
+                    "error" -> Text("Failed to read dashcam", style = MaterialTheme.typography.bodySmall, color = MaterialTheme.colorScheme.error)
+                    "" -> Text("Tap Refresh to scan", style = MaterialTheme.typography.bodySmall, color = MaterialTheme.colorScheme.onSurfaceVariant)
+                    else -> Text(dashcamStatus, style = MaterialTheme.typography.bodySmall)
+                }
+            }
+        }
+
         // Header card
         Card(
             modifier = Modifier

android/app/src/main/java/com/yarisobd/app/DashcamViewModel.kt

@@ -10,6 +10,8 @@ import androidx.work.WorkManager
 import androidx.work.workDataOf
 import com.yarisobd.app.data.CredentialStore
 import com.yarisobd.app.data.remote.PiApi
+import com.yarisobd.app.data.remote.dto.DashcamFile
+import com.yarisobd.app.data.remote.dto.DashcamFilesResponse
 import com.yarisobd.app.data.remote.dto.VideoFile
 import com.yarisobd.app.data.remote.dto.VideoListResponse
 import kotlinx.coroutines.flow.MutableSharedFlow
@@ -92,6 +94,16 @@ class DashcamViewModel(application: Application) : AndroidViewModel(application)
     private val _uploadProgress = MutableStateFlow<Map<String, ActiveDownload>>(emptyMap())
     val uploadProgress: StateFlow<Map<String, ActiveDownload>> = _uploadProgress.asStateFlow()
 
+    // USB dashcam state
+    private val _dashcamFiles = MutableStateFlow<List<DashcamFile>>(emptyList())
+    val dashcamFiles: StateFlow<List<DashcamFile>> = _dashcamFiles.asStateFlow()
+    private val _dashcamTotalSize = MutableStateFlow(0L)
+    val dashcamTotalSize: StateFlow<Long> = _dashcamTotalSize.asStateFlow()
+    private val _dashcamStatus = MutableStateFlow("")
+    val dashcamStatus: StateFlow<String> = _dashcamStatus.asStateFlow()
+    private val _dashcamLoading = MutableStateFlow(false)
+    val dashcamLoading: StateFlow<Boolean> = _dashcamLoading.asStateFlow()
+
     private fun getDownloadDir(): File {
         // Public Movies/yaris-obd/ — visible in file managers
         val dir = File(
@@ -124,6 +136,46 @@ class DashcamViewModel(application: Application) : AndroidViewModel(application)
         }
     }
 
+    fun loadDashcamFiles() {
+        viewModelScope.launch {
+            _dashcamLoading.value = true
+            try {
+                val resp: DashcamFilesResponse = api.listDashcamFiles()
+                _dashcamStatus.value = resp.status
+                _dashcamFiles.value = resp.files
+                _dashcamTotalSize.value = resp.total_size
+            } catch (e: Exception) {
+                _dashcamStatus.value = "error"
+                _downloadEvents.emit("Dashcam: ${e.message}")
+            } finally {
+                _dashcamLoading.value = false
+            }
+        }
+    }
+
+    fun deleteDashcamFile(file: DashcamFile) {
+        viewModelScope.launch {
+            try {
+                api.deleteDashcamFile(mapOf("path" to file.path))
+                _downloadEvents.emit("✓ Deleted from dashcam: ${file.path}")
+                loadDashcamFiles()
+            } catch (e: Exception) {
+                _downloadEvents.emit("✗ Delete failed: ${e.message}")
+            }
+        }
+    }
+
+    fun importDashcamFiles(paths: List<String>?) {
+        viewModelScope.launch {
+            try {
+                api.importDashcamFiles(mapOf("paths" to (paths ?: emptyList())))
+                _downloadEvents.emit("⏳ Import started")
+            } catch (e: Exception) {
+                _downloadEvents.emit("✗ Import failed: ${e.message}")
+            }
+        }
+    }
+
     fun downloadVideo(video: VideoFile) {
         val url = "$baseUrl/api/local-video/file?path=${video.path}"
         val filename = video.path.substringAfterLast("/")

android/app/src/main/java/com/yarisobd/app/MainActivity.kt

@@ -62,6 +62,10 @@ fun YarisMainScreen(client: OkHttpClient) {
     val activeDownloads by dashcamVm.activeDownloads.collectAsState()
     val deletingNames by dashcamVm.deletingNames.collectAsState()
     val uploadProgress by dashcamVm.uploadProgress.collectAsState()
+    val dashcamFiles by dashcamVm.dashcamFiles.collectAsState()
+    val dashcamTotalSize by dashcamVm.dashcamTotalSize.collectAsState()
+    val dashcamStatus by dashcamVm.dashcamStatus.collectAsState()
+    val dashcamLoading by dashcamVm.dashcamLoading.collectAsState()
     val context = androidx.compose.ui.platform.LocalContext.current
     val credentialsConfigured = com.yarisobd.app.data.CredentialStore.isConfigured(context)
 
@@ -109,9 +113,15 @@ fun YarisMainScreen(client: OkHttpClient) {
                     isLoading = isLoading,
                     error = error,
                     downloadProgress = downloadProgress,
-                    onRefresh = { dashcamVm.loadVideos() },
+                    dashcamFiles = dashcamFiles,
+                    dashcamTotalSize = dashcamTotalSize,
+                    dashcamStatus = dashcamStatus,
+                    dashcamLoading = dashcamLoading,
+                    onRefresh = { dashcamVm.loadVideos(); dashcamVm.loadDashcamFiles() },
                     onDownload = { dashcamVm.downloadVideo(it) },
                     onDelete = { dashcamVm.deleteVideo(it) },
+                    onDeleteDashcam = { dashcamVm.deleteDashcamFile(it) },
+                    onImport = { dashcamVm.importDashcamFiles(it) },
                 )
                 1 -> DownloadsScreen(
                     files = downloadedFiles,

android/app/src/main/java/com/yarisobd/app/data/remote/PiApi.kt

@@ -1,5 +1,6 @@
 package com.yarisobd.app.data.remote
 
+import com.yarisobd.app.data.remote.dto.DashcamFilesResponse
 import com.yarisobd.app.data.remote.dto.GpsStatus
 import com.yarisobd.app.data.remote.dto.VideoListResponse
 import kotlinx.serialization.json.JsonObject
@@ -7,6 +8,7 @@ import okhttp3.ResponseBody
 import retrofit2.http.Body
 import retrofit2.http.GET
 import retrofit2.http.HTTP
+import retrofit2.http.POST
 import retrofit2.http.Query
 import retrofit2.http.Streaming
 
@@ -33,6 +35,20 @@ interface PiApi {
     suspend fun getThumbnail(@Query("path") path: String): ResponseBody
 
     /** Delete local copy only */
+
+    // --- USB dashcam endpoints ---
+
+    /** List files on USB dashcam (Phase 16) */
+    @GET("/api/dash/files")
+    suspend fun listDashcamFiles(): DashcamFilesResponse
+
+    /** Delete a single file from USB dashcam */
+    @HTTP(method = "DELETE", path = "/api/dash/file", hasBody = true)
+    suspend fun deleteDashcamFile(@Body body: Map<String, String>): JsonObject
+
+    /** Import files from USB dashcam (selected or all) */
+    @POST("/api/dash/import")
+    suspend fun importDashcamFiles(@Body body: Map<String, List<String>>): JsonObject
     @HTTP(method = "DELETE", path = "/api/local-video", hasBody = true)
     suspend fun deleteVideo(@Body body: Map<String, String>): JsonObject
 }

android/app/src/main/java/com/yarisobd/app/data/remote/dto/DashcamFilesResponse.kt

@@ -0,0 +1,30 @@
+package com.yarisobd.app.data.remote.dto
+
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class DashcamFilesResponse(
+    val status: String = "",
+    val message: String? = null,
+    val device: DashcamDevice? = null,
+    val files: List<DashcamFile> = emptyList(),
+    val count: Int = 0,
+    val total_size: Long = 0,
+    val errors: List<String> = emptyList(),
+)
+
+@Serializable
+data class DashcamDevice(
+    val path: String = "",
+    val fstype: String = "",
+    val label: String? = null,
+    val size: String? = null,
+    val mountpoint: String? = null,
+)
+
+@Serializable
+data class DashcamFile(
+    val path: String = "",
+    val size: Long = 0,
+    val modified: Double = 0.0,
+)