fix: anchor SchemaMenu dropdown to its trigger button

The Rename/Drop menu used absolute positioning without a relative
parent, so it rendered at the far right of the viewport instead of
below the ⋮ button.

desktop/src/components/db-viewer/SchemaMenu.tsx

@@ -99,7 +99,7 @@ export function SchemaMenu({ connectionId, schema, onRefresh }: SchemaMenuProps)
     "w-full bg-surface border border-border rounded-md px-3 py-2 text-sm text-text placeholder:text-text-muted outline-none focus:border-accent/50 transition-colors";
 
   return (
-    <div className="flex items-center gap-1" ref={menuRef}>
+    <div className="relative flex items-center gap-1" ref={menuRef}>
       <button
         aria-label="New schema"
         onClick={() => {