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>

iosApp/iosApp/PushNotifications/PushNotificationManager.swift

@@ -388,7 +388,6 @@ class PushNotificationManager: NSObject, ObservableObject {
                     notes: nil,
                     actualCost: nil,
                     rating: nil,
-                    imageUrls: nil,
                     uploadIds: nil
                 )
                 let result = try await APILayer.shared.createTaskCompletion(request: request)