feat(translate): add WebSocket endpoint for real-time run progress

Backend:
- Add /ws/translate/run/{run_id} WebSocket endpoint in app.py
- Streams structured run status every second (total_records,
  successful_records, failed_records, progressPct, batch_count, etc.)
- Auto-detects terminal states (COMPLETED, FAILED, CANCELLED) and closes
- Authenticated via JWT/API key token query param

Frontend:
- Add getTranslateRunWsUrl() URL builder in api.js
- Update translationRunStore to use WebSocket instead of log stream
- WebSocket receives structured status JSON, updates store reactively
- Falls back to polling silently if WebSocket fails
- Keep polling as fallback for insert phase

backend/src/app.py

@@ -624,6 +624,55 @@ async def dataset_websocket_endpoint(websocket: WebSocket, env_id: str):
             task_manager.unsubscribe_dataset_events(env_id, queue)
             logger.reflect("Released dataset event subscription", extra={"env_id": env_id})
 # #endregion dataset_websocket_endpoint
+# #region translate_run_websocket [C:3] [TYPE Function]
+# @BRIEF WebSocket endpoint for translation run progress — streams structured status updates.
+# @PRE run_id must be a valid translation run ID. WebSocket authenticated via `token` query param.
+# @POST Streams run status JSON every second until terminal state or disconnect.
+# @SIDE_EFFECT Queries DB each tick for current run status via TranslationOrchestrator.
+# @UX_STATE Streaming -> Terminal (completed/failed/cancelled) -> Close
+# @UX_FEEDBACK Client receives {status, total_records, successful_records, failed_records, progressPct, ...}
+@app.websocket("/ws/translate/run/{run_id}")
+async def translate_run_websocket(websocket: WebSocket, run_id: str):
+    seed_trace_id()
+    if not await _authenticate_websocket(websocket, "ws/translate/run"):
+        await websocket.close(code=4001, reason="Authentication required")
+        return
+    await websocket.accept()
+    logger.reason("Accepted translate run WebSocket", extra={"run_id": run_id})
+    try:
+        config_manager = get_config_manager()
+        while True:
+            try:
+                from sqlalchemy.orm import Session
+                from .core.database import SessionLocal
+                from .plugins.translate.orchestrator_aggregator import TranslationResultAggregator
+                from .core.event_log import EventLog
+                db = SessionLocal()
+                try:
+                    event_log = EventLog(db)
+                    aggregator = TranslationResultAggregator(db, event_log)
+                    status = aggregator.get_run_status(run_id)
+                    total = status.get("total_records", 0) or 0
+                    done = (status.get("successful_records", 0) or 0) + (status.get("failed_records", 0) or 0) + (status.get("skipped_records", 0) or 0)
+                    progress_pct = round((done / total) * 100) if total > 0 else 0
+                    status["progressPct"] = progress_pct
+                    await websocket.send_json(status)
+                    if status.get("status") in ("COMPLETED", "FAILED", "CANCELLED"):
+                        await asyncio.sleep(2)
+                        break
+                finally:
+                    db.close()
+            except Exception as tick_err:
+                logger.explore("Translate run WS tick error", extra={"run_id": run_id, "error": str(tick_err)})
+                await websocket.send_json({"error": str(tick_err)})
+                break
+            await asyncio.sleep(1)
+    except WebSocketDisconnect:
+        logger.reason("Translate run WS disconnected", extra={"run_id": run_id})
+    except Exception as exc:
+        logger.explore("Translate run WS error", extra={"run_id": run_id, "error": str(exc)})
+    logger.reflect("Translate run WS closed", extra={"run_id": run_id})
+# #endregion translate_run_websocket
 # #region StaticFiles [C:1] [TYPE Mount] [SEMANTICS static, frontend, spa]
 # @BRIEF Mounts the frontend build directory to serve static assets.
 frontend_path = project_root / "frontend" / "build"