Add real-time WebSocket task progress with multi-job drawer

Replace 5s HTTP polling with WebSocket-based real-time updates for task
progress. Celery workers publish progress to Redis pub/sub channels;
a FastAPI WebSocket endpoint subscribes and forwards to the browser.
Polling is kept as a 30s fallback when WebSocket is unavailable.

The task progress drawer now supports multiple concurrent jobs with a
tab bar for switching between scrape and POI distance tasks.

Backend:
- Add services/task_progress_publisher.py (Redis pub/sub bridge)
- Add api/ws_routes.py (WebSocket endpoint with JWT auth)
- Publish progress from listing_tasks and poi_tasks
- Publish REVOKED via pub/sub on cancel/clear to fix stuck UI

Frontend:
- Add useTaskWebSocket hook with reconnection and keepalive
- Add TaskState and WS message types
- TaskIndicator: WS-driven updates with polling fallback
- TaskProgressDrawer: multi-job tabs, POI phase timeline
- Guard against WS overwriting local cancel state

services/task_service.py

@@ -177,11 +177,19 @@ def cancel_task(task_id: str, user_email: str | None = None) -> bool:
     """
     # Lazy import: celery_app bootstraps the broker connection.
     from celery_app import app as celery_app
+    from services.task_progress_publisher import publish_task_progress
 
     logger.info("Cancelling task %s (user=%s)", task_id, user_email)
     # Revoke the task in Celery
     celery_app.control.revoke(task_id, terminate=True)
 
+    # Publish REVOKED status via pub/sub so WebSocket clients learn immediately
+    publish_task_progress(task_id, "REVOKED", {
+        "phase": "completed",
+        "progress": 0,
+        "message": "Task cancelled",
+    })
+
     # Also remove from user's task list if user_email provided
     if user_email:
         remove_task_from_user(user_email, task_id)
@@ -222,6 +230,7 @@ def clear_all_tasks(user_email: str, revoke: bool = True) -> int:
     # Lazy imports: see get_user_tasks and cancel_task for rationale.
     from redis_repository import RedisRepository
     from celery_app import app as celery_app
+    from services.task_progress_publisher import publish_task_progress
 
     redis_repo = RedisRepository.instance()
     user = _make_system_user(user_email)
@@ -238,5 +247,11 @@ def clear_all_tasks(user_email: str, revoke: bool = True) -> int:
                 logger.warning(
                     "Failed to revoke task %s: %s", task_id, e
                 )
+            # Publish REVOKED via pub/sub so WebSocket clients learn immediately
+            publish_task_progress(task_id, "REVOKED", {
+                "phase": "completed",
+                "progress": 0,
+                "message": "Task cancelled",
+            })
 
     return redis_repo.clear_tasks_for_user(user)