feat: add retention policy and stability verification

internal/storage/mysql/baseline.sql

@@ -1,4 +1,4 @@
--- Orbit fresh-install baseline, generated from migration version 28.
+-- Orbit fresh-install baseline, generated from migration version 30.
 -- This file intentionally contains no database-level relation constraints.
 CREATE TABLE `orbit_application_resources` (
   `application_id` binary(16) NOT NULL COMMENT '所属应用标识及主键，跨命名空间共享额度',
@@ -852,3 +852,29 @@ CREATE TABLE orbit_console_sessions (
     KEY ix_console_session_expiry (expires_at, revoked_at),
     CONSTRAINT ck_console_sessions_0 CHECK (expires_at > created_at)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_as_cs COMMENT='控制台 HttpOnly 登录会话，只保存令牌摘要';
+
+-- 命名空间级历史保留策略；只保存窗口和开关，不执行自动删除。
+-- 归档执行器必须在独立事务中核对状态、备份和归档证明后再使用这些窗口。
+CREATE TABLE orbit_retention_policies (
+    namespace_id BINARY(16) NOT NULL COMMENT '策略所属命名空间，服务端核对登录会话后使用',
+    revision BIGINT UNSIGNED NOT NULL DEFAULT 1 COMMENT '策略乐观并发版本，从1开始；首次默认策略未落库时版本为0',
+    enabled BOOLEAN NOT NULL DEFAULT FALSE COMMENT '是否允许归档执行器使用策略；默认关闭，不触发删除',
+    idempotency_days INT UNSIGNED NOT NULL DEFAULT 90 COMMENT '请求幂等记录至少保留天数，范围90至3650',
+    task_history_days INT UNSIGNED NOT NULL DEFAULT 365 COMMENT '终态任务和执行证据至少保留天数，范围1至3650',
+    workflow_history_days INT UNSIGNED NOT NULL DEFAULT 365 COMMENT '终态流程、步骤、等待和流程事件至少保留天数，范围1至3650',
+    event_log_days INT UNSIGNED NOT NULL DEFAULT 365 COMMENT '状态事件和结果事件至少保留天数，范围1至3650',
+    delivery_history_days INT UNSIGNED NOT NULL DEFAULT 90 COMMENT '已确认结果交付至少保留天数，未确认交付不得按窗口清理',
+    inbox_history_days INT UNSIGNED NOT NULL DEFAULT 90 COMMENT '已处理流程Inbox事件至少保留天数，未处理记录不得清理',
+    audit_log_days INT UNSIGNED NOT NULL DEFAULT 2555 COMMENT '管理审计至少保留天数，普通清理不得处理审计记录',
+    created_at DATETIME(6) NOT NULL DEFAULT CURRENT_TIMESTAMP(6) COMMENT '策略首次保存时间，统一UTC',
+    updated_at DATETIME(6) NOT NULL DEFAULT CURRENT_TIMESTAMP(6) COMMENT '策略最后修改时间，统一UTC',
+    PRIMARY KEY (namespace_id),
+    CONSTRAINT ck_retention_policy_revision CHECK (revision > 0),
+    CONSTRAINT ck_retention_policy_idempotency CHECK (idempotency_days BETWEEN 90 AND 3650),
+    CONSTRAINT ck_retention_policy_task CHECK (task_history_days BETWEEN 1 AND 3650),
+    CONSTRAINT ck_retention_policy_workflow CHECK (workflow_history_days BETWEEN 1 AND 3650),
+    CONSTRAINT ck_retention_policy_event CHECK (event_log_days BETWEEN 1 AND 3650),
+    CONSTRAINT ck_retention_policy_delivery CHECK (delivery_history_days BETWEEN 1 AND 3650),
+    CONSTRAINT ck_retention_policy_inbox CHECK (inbox_history_days BETWEEN 1 AND 3650),
+    CONSTRAINT ck_retention_policy_audit CHECK (audit_log_days BETWEEN 1 AND 3650)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_as_cs COMMENT='命名空间历史数据保留策略，只配置窗口和开关，不自动删除';