Add cancel job button and improve jobs table UI

- Remove "All Jobs" title
- Move Status column to front of table
- Add Cancel button for in-progress jobs
- Add cancel endpoint: POST /pypi/cache/cancel/{package_name}
- Add btn-danger CSS styling

backend/app/pypi_proxy.py

@@ -34,6 +34,7 @@ from .pypi_cache_worker import (
     get_recent_activity,
     retry_failed_task,
     retry_all_failed_tasks,
+    cancel_cache_task,
 )
 
 logger = logging.getLogger(__name__)
@@ -924,3 +925,26 @@ async def pypi_cache_retry_all(
     """
     count = retry_all_failed_tasks(db)
     return {"message": f"Queued {count} tasks for retry", "count": count}
+
+
+@router.post("/cache/cancel/{package_name}")
+async def pypi_cache_cancel(
+    package_name: str,
+    db: Session = Depends(get_db),
+    _current_user: User = Depends(require_admin),
+):
+    """
+    Cancel an in-progress or pending cache task.
+
+    Args:
+        package_name: The package name to cancel.
+
+    Requires admin privileges.
+    """
+    task = cancel_cache_task(db, package_name)
+    if not task:
+        raise HTTPException(
+            status_code=404,
+            detail=f"No active cache task found for package '{package_name}'"
+        )
+    return {"message": f"Cancelled task for {task.package_name}", "task_id": str(task.id)}