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/messages/de.json

@@ -362,7 +362,13 @@
     "no_case_selected": "Kein Testfall ausgewählt",
     "case_detail": "Testfall-Details",
     "comments": "Kommentare",
-    "history": "Verlauf"
+    "history": "Verlauf",
+    "test_record": "Testnachweis",
+    "download": "Herunterladen",
+    "delete": "Löschen",
+    "click_to_upload": "Zum Hochladen klicken",
+    "or_drag_and_drop": " oder per Drag & Drop",
+    "max_file_size": "Max. Dateigröße"
   },
   "Comments": {
     "comments": "Kommentare",

frontend/messages/en.json

@@ -362,7 +362,13 @@
     "no_case_selected": "No test case selected",
     "case_detail": "Test case detail",
     "comments": "Comments",
-    "history": "History"
+    "history": "History",
+    "test_record": "Test record",
+    "download": "Download",
+    "delete": "Delete",
+    "click_to_upload": "Click to upload",
+    "or_drag_and_drop": " or drag and drop",
+    "max_file_size": "Max. file size"
   },
   "Comments": {
     "comments": "Comments",

frontend/messages/ja.json

@@ -362,7 +362,13 @@
     "no_case_selected": "テストケースが選択されていません",
     "case_detail": "テストケース詳細",
     "comments": "コメント",
-    "history": "履歴"
+    "history": "履歴",
+    "test_record": "テスト記録",
+    "download": "ダウンロード",
+    "delete": "削除",
+    "click_to_upload": "クリックしてアップロード",
+    "or_drag_and_drop": "またはドラッグアンドドロップ",
+    "max_file_size": "最大ファイルサイズ"
   },
   "Comments": {
     "comments": "コメント",

frontend/messages/pt-BR.json

@@ -362,7 +362,13 @@
     "no_case_selected": "Nenhum caso de teste selecionado",
     "case_detail": "Detalhe do caso de teste",
     "comments": "Comentários",
-    "history": "Histórico"
+    "history": "Histórico",
+    "test_record": "Registro de teste",
+    "download": "Baixar",
+    "delete": "Excluir",
+    "click_to_upload": "Clique para enviar",
+    "or_drag_and_drop": " ou arraste e solte",
+    "max_file_size": "Tamanho máx. do arquivo"
   },
   "Comments": {
     "comments": "Comentários",

frontend/messages/zh-CN.json

@@ -362,7 +362,13 @@
     "no_case_selected": "未选择测试用例",
     "case_detail": "测试用例详情",
     "comments": "评论",
-    "history": "历史"
+    "history": "历史",
+    "test_record": "测试记录",
+    "download": "下载",
+    "delete": "删除",
+    "click_to_upload": "点击上传",
+    "or_drag_and_drop": " 或拖拽文件到此处",
+    "max_file_size": "最大文件大小"
   },
   "Comments": {
     "comments": "评论",

frontend/messages/zh-TW.json

@@ -362,7 +362,13 @@
     "no_case_selected": "未選擇測試案例",
     "case_detail": "測試案例詳情",
     "comments": "留言",
-    "history": "歷史"
+    "history": "歷史",
+    "test_record": "測試紀錄",
+    "download": "下載",
+    "delete": "刪除",
+    "click_to_upload": "點擊上傳",
+    "or_drag_and_drop": " 或將檔案拖曳至此處",
+    "max_file_size": "檔案大小上限"
   },
   "Comments": {
     "comments": "留言",