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。

apps/api/migrations/0063_security_event_connections.sql

@@ -0,0 +1,40 @@
+CREATE TABLE IF NOT EXISTS gateway_security_event_connections (
+  connection_id uuid PRIMARY KEY,
+  singleton boolean NOT NULL DEFAULT true UNIQUE CHECK (singleton),
+  transmitter_issuer text NOT NULL,
+  endpoint_url text NOT NULL,
+  audience text,
+  stream_id uuid,
+  credential_ref text NOT NULL,
+  next_credential_ref text,
+  lifecycle_status text NOT NULL,
+  version bigint NOT NULL DEFAULT 1,
+  last_error_category text,
+  idempotency_key text NOT NULL,
+  created_at timestamptz NOT NULL DEFAULT now(),
+  updated_at timestamptz NOT NULL DEFAULT now(),
+  CONSTRAINT gateway_security_event_connection_status CHECK (lifecycle_status IN (
+    'connecting','verifying','bootstrap','enabled','degraded','rotating',
+    'disconnect_pending','retiring','error'
+  )),
+  CONSTRAINT gateway_security_event_connection_stream_pair CHECK (
+    (audience IS NULL AND stream_id IS NULL) OR (audience IS NOT NULL AND stream_id IS NOT NULL)
+  )
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_gateway_security_event_connections_idempotency
+  ON gateway_security_event_connections(idempotency_key);
+
+CREATE TABLE IF NOT EXISTS gateway_security_event_connection_idempotency (
+  operation text NOT NULL,
+  idempotency_key text NOT NULL,
+  request_hash text NOT NULL,
+  response jsonb NOT NULL,
+  created_at timestamptz NOT NULL DEFAULT now(),
+  PRIMARY KEY (operation, idempotency_key),
+  CONSTRAINT gateway_security_event_connection_idempotency_operation
+    CHECK (operation IN ('connect','verify','rotate','disconnect'))
+);
+
+CREATE INDEX IF NOT EXISTS idx_gateway_security_event_connection_idempotency_created
+  ON gateway_security_event_connection_idempotency(created_at);