Fix task API stability and Playwright runtime in Docker

backend/src/core/task_manager/manager.py

@@ -11,7 +11,7 @@ import asyncio
 import threading
 import inspect
 from concurrent.futures import ThreadPoolExecutor
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Dict, Any, List, Optional
 
 from .models import Task, TaskStatus, LogEntry, LogFilter, LogStats
@@ -329,8 +329,18 @@ class TaskManager:
             tasks = [t for t in tasks if t.plugin_id in plugin_id_set]
         if completed_only:
             tasks = [t for t in tasks if t.status in [TaskStatus.SUCCESS, TaskStatus.FAILED]]
-        # Sort by start_time descending (most recent first)
-        tasks.sort(key=lambda t: t.started_at or datetime.min, reverse=True)
+        # Sort by started_at descending with tolerant handling of mixed tz-aware/naive values.
+        def sort_key(task: Task) -> float:
+            started_at = task.started_at
+            if started_at is None:
+                return float("-inf")
+            if not isinstance(started_at, datetime):
+                return float("-inf")
+            if started_at.tzinfo is None:
+                return started_at.replace(tzinfo=timezone.utc).timestamp()
+            return started_at.timestamp()
+
+        tasks.sort(key=sort_key, reverse=True)
         return tasks[offset:offset + limit]
     # [/DEF:get_tasks:Function]