feat(ssf): 实现安全事件一键连接与凭据托管

新增数据库驱动的 SecurityEventConnectionManager，复用 RFC 7662 机器 Client，自动完成 Discovery、Push Bearer 生成、Stream 创建、Verification、首次启用、零停机轮换和安全退役。

增加文件与 Kubernetes SecretStore、最小权限 RBAC、动态 Receiver/撤销水位/内省降级，以及系统设置管理页面。已通过全量 Go 测试、go vet、关键包竞态测试、27 个 Web 测试、类型检查、生产构建、Compose 和 Kubernetes dry-run。

packages/contracts/src/index.ts

@@ -957,6 +957,34 @@ export interface ClientCustomizationSettingsUpdateRequest {
   iconPath?: string;
 }
 
+export interface SecurityEventConnection {
+  connectionId: string;
+  transmitterIssuer: string;
+  receiverEndpoint: string;
+  audience?: string;
+  streamId?: string;
+  lifecycleStatus: 'connecting' | 'verifying' | 'bootstrap' | 'enabled' | 'degraded' | 'rotating' | 'disconnect_pending' | 'retiring' | 'error' | string;
+  healthMode: 'disabled' | 'bootstrap' | 'push_healthy' | 'introspection_fallback' | string;
+  managementClientId: string;
+  lastVerificationAt?: string;
+  lastErrorCategory?: string;
+  version: number;
+}
+
+export interface SecurityEventConnectionPrerequisites {
+  oidcConfigured: boolean;
+  introspectionClientConfigured: boolean;
+  publicBaseUrlConfigured: boolean;
+  managementClientId: string;
+}
+
+export interface SecurityEventConnectionResponse {
+  connected: boolean;
+  lifecycleStatus?: 'disconnected' | string;
+  connection?: SecurityEventConnection;
+  prerequisites?: SecurityEventConnectionPrerequisites;
+}
+
 export interface GatewayTask {
   id: string;
   kind: string;