fix: audit remediation — SSE user scoping, FK transactional safety, UI error handling

- H4: scoped SSE import progress to exact userId match; non-HTTP events excluded from all subscribers
- H2: moved PRAGMA foreign_key_check inside SQLite transaction before COMMIT; violations rollback preserving old tables
- M1: removed dead axios-style error branch from extractErrorMessage (interceptor already unwraps)
- M2: split handleSave try/catch — save errors vs reload errors shown distinctly
- M3: added provider field validation before AI config test request
- Added SSE scoping regression tests (import service + controller)
- Added FK check failure rollback test (database-migrations.spec)
- Updated controller spec expectations for userId parameter

Co-authored-by: Code Review <branch-review>

apps/admin/src/pages/Schedules/schedule-form.ts

@@ -11,7 +11,7 @@ export interface ScheduleFormValues {
 }
 
 export interface EditableSchedule {
-  id: number;
+  id?: number;
   classId: number;
   classroomId: number;
   weekDay: number;