chore: Svelte 5 syntax updates, a11y fixes, and dead CSS removal

Replace deprecated svelte:component with direct component invocation,
use span instead of label for non-input controls with role="group",
remove unused imports and dead CSS rules.

src/routes/cospend/payments/edit/[id]/+page.svelte

@@ -932,9 +932,6 @@
       align-items: stretch;
     }
 
-    .main-actions {
-      flex-direction: column;
-    }
 
     .amount-currency {
       flex-direction: column;