feat: 实现登录失败锁定功能

新增了登录失败次数统计和临时锁定机制，包括：
1. 定义登录锁定数据结构和数据库表结构
2. 实现租户级别的锁定状态持久化接口
3. 添加登录速率限制安全策略配置
4. 在登录流程中加入锁定前置检查和失败计数逻辑
5. 提供管理员手动解锁的内部API接口
6. 新增中文本地化的锁定提示文案

server/db/mysql/admin_governance_schema.go

@@ -38,6 +38,16 @@ func ensureIMAdminGovernanceTables(exec sqlExecutor) error {
 			INDEX idx_im_login_failure_type_time(failure_type, attempt_at DESC, id DESC),
 			INDEX idx_im_login_failure_request(request_id)
 		) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
+		`CREATE TABLE IF NOT EXISTS im_login_lockouts (
+			id BIGINT NOT NULL, user_id BIGINT,
+			account_hash CHAR(64) NOT NULL,
+			failed_attempts INT NOT NULL DEFAULT 0,
+			window_started_at DATETIME(3), locked_until DATETIME(3), last_attempt_at DATETIME(3),
+			created_at DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
+			updated_at DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
+			PRIMARY KEY(id), UNIQUE INDEX uk_im_login_lockouts_account(account_hash),
+			INDEX idx_im_login_lockouts_user(user_id), INDEX idx_im_login_lockouts_locked(locked_until)
+		) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
 		`CREATE TABLE IF NOT EXISTS im_message_admin_actions (
 			id BIGINT NOT NULL AUTO_INCREMENT, action_id VARCHAR(96) NOT NULL,
 			command_id VARCHAR(96) NOT NULL, conversation_type VARCHAR(16) NOT NULL,