Make entire UI mobile-friendly with responsive breakpoints

Add media queries at 480px/768px across all components: single-column
dashboard cards on phones, progressive table column hiding, smaller
typography, reduced padding, full-width toggle buttons, and compact
header. Desktop layout unchanged.

ui/src/lib/PoolOverview.svelte

@@ -272,6 +272,12 @@
       grid-template-columns: repeat(2, minmax(0, 1fr));
     }
   }
+  @media (max-width: 480px) {
+    .grid-5 {
+      grid-template-columns: 1fr;
+      gap: 0.75rem;
+    }
+  }
 
   .retarget-bar {
     height: 4px;