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/apps/agent/nginx/observability_assets_test.go

@@ -0,0 +1,35 @@
+package nginx
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestManagedObservabilityLuaIsHealthOnly(t *testing.T) {
+	t.Parallel()
+
+	files := ManagedObservabilityLuaFiles()
+	var logLua, readLua string
+	for _, file := range files {
+		switch file.Path {
+		case "log.lua":
+			logLua = file.Content
+		case "read.lua":
+			readLua = file.Content
+		}
+	}
+	if logLua == "" || readLua == "" {
+		t.Fatal("expected log.lua and read.lua")
+	}
+	// Business counters must not be written in log phase.
+	if strings.Contains(logLua, "openresty_rx_bytes") ||
+		strings.Contains(logLua, "request_count") {
+		t.Fatal("log.lua must not accumulate business counters")
+	}
+	if !strings.Contains(readLua, "connections") || !strings.Contains(readLua, "ok") {
+		t.Fatal("read.lua must expose ok + connections health snapshot")
+	}
+	if strings.Contains(readLua, "top_domains") || strings.Contains(readLua, "request_count") {
+		t.Fatal("read.lua must not expose business traffic aggregates")
+	}
+}