feat: add runtime policy and observability

src/services/quota.rs

@@ -259,7 +259,10 @@ pub async fn consume_anonymous_units(
 
     let mut conn = state.redis.clone();
 
-    let limit = state.config.anon_daily_units as i64;
+    let limit = crate::services::settings::runtime_policy(state)
+        .await?
+        .rate_limits
+        .anonymous_units_per_day as i64;
     let ttl_seconds = 48 * 60 * 60;
     let inc = units as i64;
 
@@ -299,7 +302,7 @@ pub async fn consume_anonymous_units(
     if new_value < 0 {
         return Err(AppError::new(
             ErrorCode::QuotaExceeded,
-            "匿名试用次数已用完（每日 10 次）",
+            format!("匿名试用次数已用完（每日 {limit} 次）"),
         ));
     }