refactor(uploads): drop legacy multipart helpers; route Android UI through presigned flow

The KMP shared layer's task-completion-with-images path now exclusively
uses the presigned-URL flow: each image is compressed, uploaded directly
to B2 via APILayer.uploadImage, and the resulting upload_ids are passed
to /api/task-completions/ as JSON. Bytes never traverse our API server.

Changes:
  - TaskCompletionViewModel.createTaskCompletionWithImages now does the
    presign→POST→collect-ids dance internally. The signature stays the
    same so the three Android UI call sites (TasksScreen, AllTasksScreen,
    ResidenceDetailScreen, CompleteTaskDialog, CompleteTaskScreen) need
    no changes.
  - APILayer.createTaskCompletionWithImages removed (dead).
  - TaskCompletionApi.createCompletionWithImages removed (the multipart
    HTTP helper that posted to the legacy POST /api/task-completions/
    multipart endpoint).
  - TaskCompletionCreateRequest.imageUrls field removed.
  - Three Swift call sites (CompleteTaskView, WidgetActionProcessor,
    PushNotificationManager) updated to drop the imageUrls argument.
  - Two Kotlin call sites (CompleteTaskDialog, CompleteTaskScreen) updated.

Image uploads now match WhatsApp/Slack-class architecture: client-side
compression + direct-to-storage upload + lightweight JSON entity create.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

composeApp/src/commonMain/kotlin/com/tt/honeyDue/viewmodel/TaskCompletionViewModel.kt

@@ -25,38 +25,61 @@ class TaskCompletionViewModel : ViewModel() {
     }
 
     /**
-     * Create task completion with images.
+     * Create task completion with images, using the presigned-URL upload flow.
+     *
+     * For each image: compress, presign + POST direct to B2, collect the
+     * upload_id. Once all uploads succeed, create the completion with the
+     * collected upload_ids in a single JSON request. Bytes never traverse
+     * our API server.
+     *
+     * If any individual upload fails, the whole batch fails — partial
+     * pending_uploads rows are reaped server-side by the hourly cleanup
+     * cron, so there's nothing to clean up client-side.
      *
      * @param request The completion request data
      * @param images List of ImageData (from platform-specific image pickers)
      */
     fun createTaskCompletionWithImages(
         request: TaskCompletionCreateRequest,
-        images: List<com.tt.honeyDue.platform.ImageData> = emptyList()
+        images: List<com.tt.honeyDue.platform.ImageData> = emptyList(),
     ) {
         viewModelScope.launch {
             _createCompletionState.value = ApiResult.Loading
 
-            // Compress images and prepare for upload
-            val compressedImages = images.map { ImageCompressor.compressImage(it) }
-            val imageFileNames = images.mapIndexed { index, image ->
-                // Always use .jpg extension since we compress to JPEG
-                val baseName = image.fileName.ifBlank { "completion_$index" }
-                if (baseName.endsWith(".jpg", ignoreCase = true) ||
-                    baseName.endsWith(".jpeg", ignoreCase = true)) {
-                    baseName
-                } else {
-                    // Remove any existing extension and add .jpg
-                    baseName.substringBeforeLast('.', baseName) + ".jpg"
+            val uploadIds = mutableListOf<Int>()
+            for ((index, image) in images.withIndex()) {
+                val compressed = ImageCompressor.compressImage(image)
+                val fileName = run {
+                    val base = image.fileName.ifBlank { "completion_$index" }
+                    if (base.endsWith(".jpg", ignoreCase = true) ||
+                        base.endsWith(".jpeg", ignoreCase = true)
+                    ) base else base.substringBeforeLast('.', base) + ".jpg"
+                }
+                val uploadResult = APILayer.uploadImage(
+                    category = "completion",
+                    contentType = "image/jpeg",
+                    bytes = compressed,
+                    fileName = fileName,
+                )
+                when (uploadResult) {
+                    is ApiResult.Success -> uploadIds += uploadResult.data
+                    is ApiResult.Error -> {
+                        _createCompletionState.value = ApiResult.Error(uploadResult.message, uploadResult.code)
+                        return@launch
+                    }
+                    else -> {
+                        _createCompletionState.value = ApiResult.Error("Upload failed in unexpected state")
+                        return@launch
+                    }
                 }
             }
 
-            // Use APILayer which handles DataManager updates and summary refresh
-            _createCompletionState.value = APILayer.createTaskCompletionWithImages(
-                request = request,
-                images = compressedImages,
-                imageFileNames = imageFileNames
-            )
+            val withUploads = if (uploadIds.isNotEmpty()) {
+                request.copy(uploadIds = uploadIds.toList())
+            } else {
+                request
+            }
+            _createCompletionState.value = APILayer.createTaskCompletion(withUploads)
         }
     }