增加后台会话撤销并统一拼单业务状态

apps/backend/src/db/migrations/040_admin_sessions.sql

@@ -0,0 +1,17 @@
+CREATE TABLE IF NOT EXISTS admin_sessions (
+  id BIGSERIAL PRIMARY KEY,
+  session_id TEXT NOT NULL UNIQUE,
+  user_id BIGINT NOT NULL REFERENCES admin_users(id) ON DELETE CASCADE,
+  status TEXT NOT NULL DEFAULT 'active',
+  issued_at TIMESTAMPTZ NOT NULL,
+  last_seen_at TIMESTAMPTZ NOT NULL,
+  expires_at TIMESTAMPTZ NOT NULL,
+  revoked_at TIMESTAMPTZ,
+  created_at TIMESTAMPTZ NOT NULL,
+  updated_at TIMESTAMPTZ NOT NULL
+);
+
+CREATE INDEX IF NOT EXISTS idx_admin_sessions_user_status
+  ON admin_sessions(user_id, status, expires_at DESC);
+
+COMMENT ON TABLE admin_sessions IS '后台登录会话，支持单设备退出和服务端撤销';