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>

config/example.toml

@@ -77,6 +77,7 @@ path = "logs/webhook_delivery.jsonl"
 enabled = false
 event_url = ""
 case_url = ""
+source_id = ""
 callback_token = ""
 connect_timeout_seconds = 3
 read_timeout_seconds = 5