Migrate Auth/Contractor/Document/Notification/Subscription services to ctx

Every public method on these five services now takes ctx context.Context as
the first arg and routes its repo calls through .WithContext(ctx). With
TaskService and ResidenceService already migrated, this means every
in-process service that touches Postgres now produces a flame graph in
Jaeger where the SQL spans nest under the parent HTTP request span.

Endpoints now fully traced (HTTP → service → SQL):
- /api/auth/login, /register, /logout, /me, /verify-email, /resend-verification
- /api/auth/forgot-password, /verify-reset, /reset-password, /update-profile
- /api/contractors/* (CRUD + favorite + by-residence + tasks)
- /api/documents/* (CRUD + activate/deactivate + image upload/delete)
- /api/notifications/* (list, count, mark-read, prefs, devices)
- /api/subscription/* (status, purchase, cancel, triggers, promotions)
- All previously-migrated /api/tasks/* and /api/residences/* paths

Internal helpers also threaded:
- TaskService.sendTaskCompletedNotification → forwards ctx
- TaskService.UpdateUserTimezone → forwards ctx to NotificationService
- ResidenceService.CreateResidence → forwards ctx to SubscriptionService.CheckLimit
- NotificationService.registerAPNSDevice / registerGCMDevice → both take ctx

~75 method signatures, ~120 handler/test call sites updated. Tests pass
green; the only failure is the pre-existing flaky TaskHandler_QuickComplete
SQLite race that fails ~60% of runs on master.

Step 3 of the observability plan is now genuinely complete: every API
endpoint backed by a Go service emits a per-request flame graph with
HTTP → service → SQL spans, plus B2/APNs/FCM/asynq spans where applicable.

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

internal/services/task_service.go

@@ -898,7 +898,7 @@ func (s *TaskService) sendTaskCompletedNotification(ctx context.Context, task *m
 		// Send email notification (to everyone INCLUDING the person who completed it)
 		// Check user's email notification preferences first
 		if s.emailService != nil && user.Email != "" && s.notificationService != nil {
-			prefs, prefsErr := s.notificationService.GetPreferences(user.ID)
+			prefs, prefsErr := s.notificationService.GetPreferences(ctx, user.ID)
 			// LE-06: Log fail-open behavior when preferences cannot be loaded
 			if prefsErr != nil {
 				log.Warn().
@@ -1264,8 +1264,8 @@ func (s *TaskService) GetFrequencies(ctx context.Context) ([]responses.TaskFrequ
 // UpdateUserTimezone updates the user's timezone for background job calculations.
 // This is called from handlers when the X-Timezone header is present.
 // Delegates to NotificationService since timezone is stored in notification preferences.
-func (s *TaskService) UpdateUserTimezone(userID uint, timezone string) {
+func (s *TaskService) UpdateUserTimezone(ctx context.Context, userID uint, timezone string) {
 	if s.notificationService != nil {
-		s.notificationService.UpdateUserTimezone(userID, timezone)
+		s.notificationService.UpdateUserTimezone(ctx, userID, timezone)
 	}
 }