fix(ui): resolve Select dropdown not appearing in FullScreenPanel

- Increase SelectContent z-index from z-50 to z-[100] to appear above FullScreenPanel (z-[60])
- Replace form.watch() with form.getValues() in useCallback handlers for correct react-hook-form usage
- Remove max-w-[56rem] constraints from various panels for consistent full-width layout

src/components/settings/SettingsPage.tsx

@@ -202,7 +202,7 @@ export function SettingsPage({
   };
 
   return (
-    <div className="mx-auto max-w-[56rem] flex flex-col h-[calc(100vh-8rem)] overflow-hidden px-6">
+    <div className="flex flex-col h-[calc(100vh-8rem)] overflow-hidden px-6">
       {isBusy ? (
         <div className="flex flex-1 items-center justify-center">
           <Loader2 className="h-8 w-8 animate-spin text-muted-foreground" />