fix(System): correct memory usage percentage calculation

The percentage was using (total - available) / total which excludes
reclaimable buffers/cache, but the displayed "Used RAM" value uses
mem.used which includes them. This mismatch showed 14% alongside
22 GB / 62 GB. Now uses mem.used / mem.total so the percentage
matches the displayed numbers.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 2 people

admin/inertia/pages/settings/system.tsx

@@ -18,7 +18,7 @@ export default function SettingsPage(props: {
   })
 
   const memoryUsagePercent = info?.mem.total
-    ? (((info.mem.total - info.mem.available) / info.mem.total) * 100).toFixed(1)
+    ? ((info.mem.used / info.mem.total) * 100).toFixed(1)
     : 0
 
   const swapUsagePercent = info?.mem.swaptotal