perf(usage): user-me usage 查询避免全量加载，默认限制 7 天范围

- UsageAuditListQuery 新增 limit 字段，支持在 SQL 层 LIMIT
- user-me usage 端点无时间范围时默认查最近 7 天
- active usage 端点无 ids 过滤时限制查最近 1 小时
- InMemory 实现同步支持 limit truncate

crates/aether-data/src/repository/usage/memory.rs

@@ -214,6 +214,9 @@ impl UsageReadRepository for InMemoryUsageReadRepository {
                 .cmp(&right.created_at_unix_ms)
                 .then_with(|| left.request_id.cmp(&right.request_id))
         });
+        if let Some(limit) = query.limit {
+            items.truncate(limit);
+        }
         Ok(items)
     }
 

crates/aether-data/src/repository/usage/sql.rs

@@ -1213,6 +1213,9 @@ impl SqlxUsageReadRepository {
         }
 
         builder.push(" ORDER BY \"usage\".created_at ASC, \"usage\".request_id ASC");
+        if let Some(limit) = query.limit {
+            builder.push(" LIMIT ").push_bind(limit as i64);
+        }
         let query = builder.build();
         let mut rows = query.fetch(&self.pool);
         let mut items = Vec::new();