feat: video analysis switched to push mode (upload whole video, sync response)

Rationale: Oracle cannot reach NAS (Tailscale userspace mode on NAS, no TUN),
the old pull+webhook design requires Edge to download video from NAS and
callback to NAS - both blocked. New design is one-way NAS -> Oracle:

- FAM-Edge: new POST /api/edge/video/push endpoint accepts multipart video
  upload, reuses existing OpenCV scene-change keyframe selection, analyzes
  synchronously and returns the result payload directly in the HTTP response
  (no webhook callback). Old /api/edge/video/analyze kept for compatibility.
- FAM-Edge: VideoPreprocessor.save_upload() saves the uploaded file
- FAM-Edge: AIOrchestrator.process_push_task() runs the full pipeline
  (health check -> extract -> select -> compress -> VLM -> fusion) and
  returns callback-style payload dict
- FAM-Core: Dispatcher rewritten to push mode - reads local video file,
  uploads with task metadata (camera_name, event_start_time from file mtime,
  known_members_context), applies the result to DB via shared
  event_receiver.apply_success_event()
- FAM-Core: event_receiver success logic extracted into reusable
  apply_success_event() (used by both webhook route and dispatcher)
- config: edge_url -> /api/edge/video/push, push_timeout 1800s, gunicorn
  Edge timeout raised to 1800s for long synchronous analysis

fam-edge/src/fam_edge/api_gateway/api_gateway.py

@@ -9,6 +9,7 @@ from flask import Blueprint, request, jsonify
 
 from ..logger import setup_logger
 from ..ai_orchestrator.orchestrator import AIOrchestrator
+from ..video_preprocessor.preprocessor import VideoPreprocessor
 
 logger = setup_logger('fam-edge.api_gateway')
 
@@ -71,6 +72,63 @@ def receive_task():
     return jsonify({"status": "accepted", "task_id": task_id}), 202
 
 
+@api_bp.route('/api/edge/video/push', methods=['POST'])
+def receive_push_task():
+    """推送模式：接收 multipart 视频上传，同步分析，结果随 HTTP 响应返回
+
+    NAS 无法被 Oracle 反向访问（Tailscale 不通），因此改为 NAS 主动上传视频，
+    Edge 用 OpenCV 场景变化检测抽帧后分析，摘要直接放在响应里带回。
+    """
+    global _currently_processing
+
+    task_id_raw = request.form.get('task_id')
+    file = request.files.get('video')
+    if not task_id_raw or not file:
+        return jsonify({"error": "缺少必填字段: task_id, video"}), 400
+
+    try:
+        task_id = int(task_id_raw)
+    except ValueError:
+        return jsonify({"error": "task_id 必须是整数"}), 400
+
+    logger.info(f"[task_id={task_id}] 收到推送任务: {file.filename}")
+
+    # 并发控制（同步处理，占用整个请求周期）
+    with _current_task_lock:
+        if _currently_processing:
+            logger.warning(f"[task_id={task_id}] 已有任务处理中，返回 429")
+            return jsonify({"error": "Queue full", "retry_after": 60}), 429
+        _currently_processing = True
+
+    preprocessor = None
+    try:
+        preprocessor = VideoPreprocessor(task_id)
+        video_path = preprocessor.save_upload(file)
+
+        task_data = {
+            "task_id": task_id,
+            "camera_name": request.form.get('camera_name', ''),
+            "event_start_time": request.form.get('event_start_time', ''),
+            "event_end_time": request.form.get('event_end_time', ''),
+            "known_members_context": request.form.get('known_members_context', ''),
+        }
+
+        result = get_orchestrator().process_push_task(task_data, video_path, preprocessor)
+        return jsonify(result), 200
+
+    except Exception as e:
+        logger.error(f"[task_id={task_id}] 推送任务异常: {e}", exc_info=True)
+        return jsonify({
+            "task_id": task_id, "status": "failed",
+            "failure_stage": "upload", "error_message": str(e)
+        }), 200
+    finally:
+        if preprocessor is not None:
+            preprocessor.cleanup()
+        with _current_task_lock:
+            _currently_processing = False
+
+
 @api_bp.route('/health', methods=['GET'])
 def health():
     """健康检查"""