feat(usage): add auto-refresh interval for usage queries

New Features:
- Users can configure auto-query interval in "Configure Usage Query" dialog
- Interval in minutes (0 = disabled, recommend 5-60 minutes)
- Auto-query only enabled for currently active provider
- Display last query timestamp in relative time format (e.g., "5 min ago")
- Execute first query immediately when enabled, then repeat at intervals

Technical Implementation:
- Backend: Add auto_query_interval field to UsageScript struct
- Frontend: Create useAutoUsageQuery Hook to manage timers and query state
- UI: Add auto-query interval input field in UsageScriptModal
- Integration: Display auto-query results and timestamp in UsageFooter
- i18n: Add Chinese and English translations

UX Improvements:
- Minimum interval protection (1 minute) to prevent API abuse
- Auto-cleanup timers on component unmount
- Silent failure handling for auto-queries, non-intrusive to users
- Prioritize auto-query results, fallback to manual query results
- Timestamp display positioned next to refresh button for better clarity

src-tauri/src/provider.rs

@@ -71,6 +71,10 @@ pub struct UsageScript {
     #[serde(skip_serializing_if = "Option::is_none")]
     #[serde(rename = "userId")]
     pub user_id: Option<String>,
+    /// 自动查询间隔（单位：分钟，0 表示禁用自动查询）
+    #[serde(skip_serializing_if = "Option::is_none")]
+    #[serde(rename = "autoQueryInterval")]
+    pub auto_query_interval: Option<u64>,
 }
 
 /// 用量数据