feat(obs): 访问日志 SSOT 与 edge_health，去掉协议兼容层

Agent 仅上报 host_metrics/edge_health/access_logs；业务流量与 UV 由
Server 侧访问日志聚合。新增 of_node_edge_health 与 of_access_log_hourly，
删除 request_reports/openresty 吞吐路径；API 不再暴露 traffic_reports
与 openresty_rx|tx。心跳/离线默认阈值与回填迁移一并入库。

internal/db/migrator/goose/sqlite/202607180001_update_agent_heartbeat_offline_defaults.sql

@@ -0,0 +1,27 @@
+-- +goose Up
+-- 将仍为历史默认值的心跳/离线配置升级为新默认：心跳 3s、离线 60s。
+-- 已由管理员改成其他值的配置不受影响。
+UPDATE w_system_configs
+SET value = '3000',
+    updated_at = CURRENT_TIMESTAMP
+WHERE key = 'agent_heartbeat_interval'
+  AND value = '10000';
+
+UPDATE w_system_configs
+SET value = '60000',
+    updated_at = CURRENT_TIMESTAMP
+WHERE key = 'node_offline_threshold'
+  AND value = '120000';
+
+-- +goose Down
+UPDATE w_system_configs
+SET value = '10000',
+    updated_at = CURRENT_TIMESTAMP
+WHERE key = 'agent_heartbeat_interval'
+  AND value = '3000';
+
+UPDATE w_system_configs
+SET value = '120000',
+    updated_at = CURRENT_TIMESTAMP
+WHERE key = 'node_offline_threshold'
+  AND value = '60000';