feat(gateway): 敏感操作审计日志（T4.B）

- store.AuditLog 表(sundynix_audit_log) + AppendAudit/ListAudit
- middleware.Audit(db)：只审计变更类(POST/PUT/DELETE/PATCH)，收尾 best-effort
  落库(独立超时 ctx，失败静默不拖垮主流程)；挂管理组 + prompt 激活/撤销 + HITL 审批
- GET /api/v1/admin/audit：倒序审计流(limit/offset 翻页)
- live：PUT pricing / POST prompts/deactivate 留痕(actor/path/status/ip)，GET 不记
- DEPTH_ROADMAP T4.B：overview✅ + audit✅ 打勾

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sundynix-gateway/internal/handler/admin.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"encoding/json"
 	"net/http"
+	"strconv"
 	"strings"
 	"time"
 
@@ -16,6 +17,34 @@ import (
 	"github.com/sundynix/sundynix-shared/secrets"
 )
 
+// AuditList: GET /api/v1/admin/audit?limit=&offset= —— 敏感操作审计流（倒序，供运维溯源）。
+func (h *Handler) AuditList(c *gin.Context) {
+	limit, offset := 50, 0
+	if v := c.Query("limit"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil {
+			limit = n
+		}
+	}
+	if v := c.Query("offset"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil {
+			offset = n
+		}
+	}
+	rows, err := h.db.ListAudit(c.Request.Context(), limit, offset)
+	if err != nil {
+		c.JSON(http.StatusBadGateway, gin.H{"error": err.Error()})
+		return
+	}
+	out := make([]gin.H, 0, len(rows))
+	for _, a := range rows {
+		out = append(out, gin.H{
+			"id": a.ID, "actor": a.Actor, "action": a.Action, "route": a.Route,
+			"path": a.Path, "status": a.Status, "ip": a.IP, "detail": a.Detail, "at": a.CreatedAt,
+		})
+	}
+	c.JSON(http.StatusOK, gin.H{"logs": out})
+}
+
 // AdminOverview: GET /api/v1/admin/overview —— 管理端系统级聚合（控制塔口径）。
 // 区别于 stats/overview（桌面端个人工作台）：这里一律系统级——全平台用户/任务/评测/
 // 模型配置态/提示词控制面态/服务健康。Task/Eval 表无 owner 即全量；用户/KB/Doc 走全局计数。