feat: FEAT-05 — DTC history sync to remote server

- Server: dtc_events table (migrate_phase27_dtc.sql), db.py helpers
  (upsert_dtc_snapshot, list_dtc_events, delete_dtc_event)
- Server API: POST /api/v1/dtc/batch (device auth), GET/DELETE /api/v1/portal/dtc
- Server portal: /dtc page with code, description, MIL, status, timestamps, delete
- Server nav: DTC history in sidebar + mobile bottom nav
- Pi: _upload_dtc_snapshot() in app_upload.py — uploads when snapshot changes,
  skips when OBD disconnected or unchanged

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

@@ -34,12 +34,12 @@ data class DownloadProgress(
 
 class DashcamViewModel(application: Application) : AndroidViewModel(application) {
 
-    private val baseUrl = "http://10.42.0.1/"
+    private val baseUrl = "http://10.42.0.1"  // no trailing slash
     private val okHttp = OkHttpClient.Builder().build()
     private val json = Json { ignoreUnknownKeys = true; coerceInputValues = true }
 
     private val api: PiApi = Retrofit.Builder()
-        .baseUrl(baseUrl)
+        .baseUrl("$baseUrl/")  // Retrofit requires trailing slash
         .client(okHttp)
         .addConverterFactory(json.asConverterFactory("application/json".toMediaType()))
         .build()
@@ -93,14 +93,14 @@ class DashcamViewModel(application: Application) : AndroidViewModel(application)
             val dir = app.getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS) ?: return@launch
             val localFile = File(dir, video.path.substringAfterLast("/"))
 
-            // Skip if already downloaded
+            // Skip if already downloaded and size matches
             if (localFile.exists() && localFile.length() == video.size) {
-                _downloadEvents.emit("Already downloaded: ${localFile.name}")
+                _downloadEvents.emit("✓ Already downloaded: ${localFile.name}")
                 return@launch
             }
 
             try {
-                withContext(Dispatchers.IO) {
+                val result = withContext(Dispatchers.IO) {
                     val request = Request.Builder()
                         .url("$baseUrl/api/local-video/file?path=${video.path}")
                         .get()
@@ -108,10 +108,10 @@ class DashcamViewModel(application: Application) : AndroidViewModel(application)
 
                     val response = okHttp.newCall(request).execute()
                     if (!response.isSuccessful) {
-                        throw Exception("HTTP ${response.code}")
+                        return@withContext "Download failed: HTTP ${response.code}"
                     }
 
-                    val body = response.body ?: throw Exception("Empty body")
+                    val body = response.body ?: return@withContext "Download failed: Empty body"
                     val total = body.contentLength()
                     localFile.parentFile?.mkdirs()
 
@@ -124,19 +124,19 @@ class DashcamViewModel(application: Application) : AndroidViewModel(application)
                                 if (read == -1L) break
                                 sink.write(buffer, read)
                                 downloaded += read
-                                _downloadProgress.value = _downloadProgress.value + (
-                                    video.path to DownloadProgress(video.path, downloaded, total)
-                                )
+                                val progress = DownloadProgress(video.path, downloaded, total)
+                                _downloadProgress.value = _downloadProgress.value + (video.path to progress)
                             }
                         }
                     }
 
                     _downloadProgress.value = _downloadProgress.value - video.path
-                    _downloadEvents.emit("Downloaded: ${localFile.name}")
+                    "✓ Downloaded: ${localFile.name} (${downloaded} bytes)"
                 }
+                _downloadEvents.emit(result)
             } catch (e: Exception) {
                 _downloadProgress.value = _downloadProgress.value - video.path
-                _downloadEvents.emit("Download failed: ${e.message}")
+                _downloadEvents.emit("✗ Download failed: ${e.message}")
             }
         }
     }

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

@@ -4,8 +4,8 @@ import com.yarisobd.app.data.remote.dto.GpsStatus
 import com.yarisobd.app.data.remote.dto.VideoListResponse
 import okhttp3.ResponseBody
 import retrofit2.http.Body
-import retrofit2.http.DELETE
 import retrofit2.http.GET
+import retrofit2.http.HTTP
 import retrofit2.http.Query
 import retrofit2.http.Streaming
 
@@ -32,6 +32,6 @@ interface PiApi {
     suspend fun getThumbnail(@Query("path") path: String): ResponseBody
 
     /** Delete local copy only */
-    @DELETE("/api/local-video")
+    @HTTP(method = "DELETE", path = "/api/local-video", hasBody = true)
     suspend fun deleteVideo(@Body body: Map<String, String>): Map<String, Any?>
 }