feat: add per-app usage filtering (Claude/Codex/Gemini)

Add dashboard-level app type filter to usage statistics, replacing the
DataSourceBar with a more useful segmented control. All components
(summary cards, trend chart, provider stats, model stats, request logs)
now respond to the selected app filter.

Backend: add optional app_type parameter to get_usage_summary,
get_daily_trends, get_provider_stats, and get_model_stats queries.
Frontend: new AppTypeFilter type, updated query keys with appType
dimension for proper cache separation, and RequestLogTable local
filter auto-locks when dashboard filter is active.

src-tauri/src/commands/usage.rs

@@ -11,8 +11,11 @@ pub fn get_usage_summary(
     state: State<'_, AppState>,
     start_date: Option<i64>,
     end_date: Option<i64>,
+    app_type: Option<String>,
 ) -> Result<UsageSummary, AppError> {
-    state.db.get_usage_summary(start_date, end_date)
+    state
+        .db
+        .get_usage_summary(start_date, end_date, app_type.as_deref())
 }
 
 /// 获取每日趋势
@@ -21,20 +24,29 @@ pub fn get_usage_trends(
     state: State<'_, AppState>,
     start_date: Option<i64>,
     end_date: Option<i64>,
+    app_type: Option<String>,
 ) -> Result<Vec<DailyStats>, AppError> {
-    state.db.get_daily_trends(start_date, end_date)
+    state
+        .db
+        .get_daily_trends(start_date, end_date, app_type.as_deref())
 }
 
 /// 获取 Provider 统计
 #[tauri::command]
-pub fn get_provider_stats(state: State<'_, AppState>) -> Result<Vec<ProviderStats>, AppError> {
-    state.db.get_provider_stats()
+pub fn get_provider_stats(
+    state: State<'_, AppState>,
+    app_type: Option<String>,
+) -> Result<Vec<ProviderStats>, AppError> {
+    state.db.get_provider_stats(app_type.as_deref())
 }
 
 /// 获取模型统计
 #[tauri::command]
-pub fn get_model_stats(state: State<'_, AppState>) -> Result<Vec<ModelStats>, AppError> {
-    state.db.get_model_stats()
+pub fn get_model_stats(
+    state: State<'_, AppState>,
+    app_type: Option<String>,
+) -> Result<Vec<ModelStats>, AppError> {
+    state.db.get_model_stats(app_type.as_deref())
 }
 
 /// 获取请求日志列表