feat: 添加PAYMENT_MAINTENANCE_MODE维护模式 + ServiceUnavailable错误

src/db.rs

@@ -9,11 +9,14 @@ use crate::error::AppError;
 
 // 用于插入weather_data的数据
 pub async fn insert_weather_data(pool: &PgPool, weather_data: &WeatherData, user_id: i32) -> Result<i32, AppError> {
-    // 配额检查：非付费用户数据条数限制
-    let user = get_user_by_id(pool, user_id).await?;
-    let is_paid_active = user.is_paid && user.paid_expires_at.map_or(true, |expires| expires > Utc::now());
-    
-    if !is_paid_active {
+    // 维护模式：跳过所有配额检查
+    let is_maintenance = std::env::var("PAYMENT_MAINTENANCE_MODE").ok() == Some("true".to_string());
+    if !is_maintenance {
+        // 配额检查：非付费用户数据条数限制
+        let user = get_user_by_id(pool, user_id).await?;
+        let is_paid_active = user.is_paid && user.paid_expires_at.map_or(true, |expires| expires > Utc::now());
+        
+        if !is_paid_active {
         let current_count = count_user_weather_data(pool, user_id).await?;
         let limit: i64 = env::var("FREE_USER_DATA_LIMIT")
             .unwrap_or_else(|_| "20".to_string())
@@ -24,6 +27,7 @@ pub async fn insert_weather_data(pool: &PgPool, weather_data: &WeatherData, user
             return Err(AppError::Forbidden("数据条数已达上限，请升级为付费用户".to_string()));
         }
     }
+    }
 
     // 准备插入数据的 SQL 语句
     let insert_query = r#"