feat: upload test record attachments per run case

Allow testers to attach evidence files to a single test case within a
specific test run, proving the test was actually executed. Attachments
are scoped to the RunCase (per-execution), not the shared case definition.

Backend:
- runCaseAttachments join table + model (CASCADE on runCase/attachment)
- POST/GET /runcaseattachments routes (reuse /attachments download+delete)

Frontend:
- new "Test record" tab in the run case detail pane with drag-and-drop
  upload, scoped to reporters; i18n for all 6 locales

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/types/run.ts

@@ -106,6 +106,12 @@ type RunDetailMessages = {
   caseDetail: string;
   comments: string;
   history: string;
+  testRecord: string;
+  download: string;
+  delete: string;
+  clickToUpload: string;
+  orDragAndDrop: string;
+  maxFileSize: string;
 };
 
 export type {