feat(ui): move usage display inline next to enable button

- Refactor UsageFooter to support inline mode with two-row layout
  - Row 1: Last refresh time + refresh button (right-aligned)
  - Row 2: Used + Remaining + Unit
- Update ProviderCard layout to show usage inline instead of below
- Improve text spacing: reduce gap from 1 to 0.5 for tighter label-value pairs
- Update Chinese translation: "使用" → "已使用" for better clarity
- Maintain backward compatibility with bottom display mode

This change unifies card heights and improves visual consistency
across providers with and without usage queries enabled.

src/i18n/locales/zh.json

@@ -337,7 +337,7 @@
     "planUsage": "套餐用量",
     "invalid": "已失效",
     "total": "总：",
-    "used": "使用：",
+    "used": "已使用：",
     "remaining": "剩余：",
     "justNow": "刚刚",
     "minutesAgo": "{{count}} 分钟前",