Merge branch 'refactor/backend-architecture' into development

api/migrations_legacy/add_users_subscription_columns.sql

@@ -0,0 +1,26 @@
+-- 为 users 表添加订阅相关列（subscription_type, subscription_expires_at）
+-- 若列已存在则跳过，可重复执行。
+-- 执行方式: psql -U <user> -d <database> -f api/migrations/add_users_subscription_columns.sql
+
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM information_schema.columns
+        WHERE table_schema = 'public' AND table_name = 'users' AND column_name = 'subscription_type'
+    ) THEN
+        ALTER TABLE users ADD COLUMN subscription_type VARCHAR DEFAULT 'free';
+        RAISE NOTICE '已添加 users.subscription_type 列';
+    ELSE
+        RAISE NOTICE 'users.subscription_type 列已存在，跳过';
+    END IF;
+
+    IF NOT EXISTS (
+        SELECT 1 FROM information_schema.columns
+        WHERE table_schema = 'public' AND table_name = 'users' AND column_name = 'subscription_expires_at'
+    ) THEN
+        ALTER TABLE users ADD COLUMN subscription_expires_at TIMESTAMP WITH TIME ZONE DEFAULT NULL;
+        RAISE NOTICE '已添加 users.subscription_expires_at 列';
+    ELSE
+        RAISE NOTICE 'users.subscription_expires_at 列已存在，跳过';
+    END IF;
+END $$;