feat: enrich webhook payloads with downstream event table fields

Add missing fields (event_code, camera_ip, started_at, ended_at,
dwell_seconds, is_discarded, alerted_at, etc.) to both batch_event
and case_event payloads. Introduce source_id config for payload
injection and infer_camera_ip to extract IP from RTSP stream URL.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README_zh.md

@@ -200,6 +200,7 @@ path = "logs/webhook_retry.jsonl"
 enabled = true
 event_url = "https://example.com/runtime-events"
 case_url = "https://example.com/case-events"
+source_id = "cold-display-guard"
 callback_token = "shared-secret"
 connect_timeout_seconds = 3
 read_timeout_seconds = 5
@@ -223,6 +224,16 @@ retry_max_backoff_seconds = 1800
 
 相关 webhook 字段：
 
+- `event_code`：下游事件列表可直接使用的稳定编码，当前取批次 ID
+- `camera_id` / `camera_ip`：来源设备和摄像头 IP
+- `zone_id` / `zone_label`：所属区域
+- `started_at`：开始计时时间点
+- `ended_at` / `removed_at`：取出时间点
+- `dwell_seconds`：当前批次累计计时时长
+- `is_discarded` / `discarded_at`：是否已丢弃及丢弃时间点
+- `created_at`：该条外部事件记录的创建时间
+- `alerted_at` / `alarm_at`：时长告警时间点
+- `updated_at`：该条外部事件记录的最新更新时间
 - `snapshot_upload_status`：`uploaded` 或 `error`
 - `snapshot_object_key`：上传成功后的 OSS 路径
 - `snapshot_file_name`：上传文件名