fix(event-time): event_end_time/frame_timestamp NOT NULL 列兜底

- Edge push 模式: event_end_time 未提供时用 start+视频时长推算
- fam-core db_layer: insert_event 空值兜底(end→start→NOW)
- insert_event_detail: frame_timestamp 空值兜底 NOW
解决 1048 Column cannot be null 落库失败

fam-edge/src/fam_edge/ai_orchestrator/orchestrator.py

@@ -14,6 +14,7 @@ import time
 import json
 import base64
 import requests
+from datetime import datetime, timedelta
 from concurrent.futures import ThreadPoolExecutor, as_completed, TimeoutError as FuturesTimeout
 from typing import Dict, List, Optional
 
@@ -366,6 +367,17 @@ class AIOrchestrator:
                 video_path, len(compressed_frames), event_start_time
             )
 
+            # event_end_time 未提供时，用 start + 视频时长推算（DB 列 NOT NULL）
+            event_end_time = task_data.get('event_end_time', '')
+            if not event_end_time and event_start_time and preprocessor.video_duration > 0:
+                try:
+                    start_dt = datetime.strptime(event_start_time, '%Y-%m-%d %H:%M:%S')
+                    event_end_time = (
+                        start_dt + timedelta(seconds=int(preprocessor.video_duration))
+                    ).strftime('%Y-%m-%d %H:%M:%S')
+                except ValueError:
+                    pass
+
             # 3. 并行视觉分析
             model_outputs = self.run_visual_analysis(
                 healthy_adapters, compressed_frames, frame_timestamps, known_members
@@ -383,7 +395,7 @@ class AIOrchestrator:
                 "task_id": task_id,
                 "status": "success",
                 "event_start_time": event_start_time,
-                "event_end_time": task_data.get('event_end_time', ''),
+                "event_end_time": event_end_time,
                 "camera_name": task_data.get('camera_name', ''),
                 "global_summary": fusion_result.get('global_summary', ''),
                 "entities_json": fusion_result.get('entities_json', []),