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/components/providers/ProviderCard.tsx

@@ -170,22 +170,25 @@ export function ProviderCard({
           </div>
         </div>
 
-        <ProviderActions
-          isCurrent={isCurrent}
-          onSwitch={() => onSwitch(provider)}
-          onEdit={() => onEdit(provider)}
-          onConfigureUsage={() => onConfigureUsage(provider)}
-          onDelete={() => onDelete(provider)}
-        />
-      </div>
+        <div className="flex items-center gap-3">
+          <UsageFooter
+            provider={provider}
+            providerId={provider.id}
+            appId={appId}
+            usageEnabled={usageEnabled}
+            isCurrent={isCurrent}
+            inline={true}
+          />
 
-      <UsageFooter
-        provider={provider}
-        providerId={provider.id}
-        appId={appId}
-        usageEnabled={usageEnabled}
-        isCurrent={isCurrent}
-      />
+          <ProviderActions
+            isCurrent={isCurrent}
+            onSwitch={() => onSwitch(provider)}
+            onEdit={() => onEdit(provider)}
+            onConfigureUsage={() => onConfigureUsage(provider)}
+            onDelete={() => onDelete(provider)}
+          />
+        </div>
+      </div>
     </div>
   );
 }