refactor(usage): consolidate query logic to eliminate DRY violations

Breaking Changes:
- Removed useAutoUsageQuery hook (119 lines)
- Unified all usage queries into single useUsageQuery hook

Technical Improvements:
- Eliminated duplicate state management (React Query + manual useState)
- Fixed single source of truth principle violation
- Replaced manual setInterval with React Query's built-in refetchInterval
- Reduced UsageFooter complexity by 28% (54 → 39 lines)

New Features:
- useUsageQuery now accepts autoQueryInterval option
- Automatic query interval control (0 = disabled, min 1 minute)
- Built-in lastQueriedAt timestamp from dataUpdatedAt
- Auto-query only enabled for currently active provider

Architecture Benefits:
- Single data source: manual and auto queries share same cache
- No more state inconsistency between manual/auto query results
- Leverages React Query's caching, deduplication, and background updates
- Cleaner separation of concerns

Code Changes:
- src/lib/query/queries.ts: Enhanced useUsageQuery with auto-query support
- src/components/UsageFooter.tsx: Simplified to use single query hook
- src/hooks/useAutoUsageQuery.ts: Deleted (redundant)
- All type checks passed

src/lib/api/usage.ts

@@ -6,7 +6,7 @@ import i18n from "@/i18n";
 export const usageApi = {
   async query(providerId: string, appId: AppId): Promise<UsageResult> {
     try {
-      return await invoke("query_provider_usage", {
+      return await invoke("queryProviderUsage", {
         providerId: providerId,
         app: appId,
       });
@@ -36,7 +36,7 @@ export const usageApi = {
     userId?: string
   ): Promise<UsageResult> {
     try {
-      return await invoke("test_usage_script", {
+      return await invoke("testUsageScript", {
         providerId: providerId,
         app: appId,
         scriptCode: scriptCode,
@@ -59,4 +59,3 @@ export const usageApi = {
     }
   },
 };
-