refactor: unify focus styles across all input fields

Replace inconsistent focus border styles with a unified soft blue ring effect
across all input and textarea components.

Changes:
- Add consistent focus:ring styles to Input and Textarea components
- Use focus:ring-blue-500/20 (light) and focus:ring-blue-400/20 (dark)
- Remove focus border color changes for a more subtle design
- Update ApiKeyInput to match the unified focus style
- Update all manual textarea elements (Codex and Claude configs)

Benefits:
- Consistent visual feedback across all form inputs
- Soft, elegant focus indication with blue glow effect
- No jarring border color changes
- Better user experience with subtle, professional styling

The focus effect now uses only a soft blue ring (20% opacity) without
changing border colors, creating a more refined and less distracting
interaction pattern.

src/components/ui/textarea.tsx

@@ -8,7 +8,7 @@ const Textarea = React.forwardRef<HTMLTextAreaElement, TextareaProps>(
     return (
       <textarea
         className={cn(
-          "flex min-h-[80px] w-full rounded-md border border-border-default bg-background px-3 py-2 text-sm shadow-sm placeholder:text-muted-foreground focus-visible:outline-none focus-visible:border-border-active disabled:cursor-not-allowed disabled:opacity-50",
+          "flex min-h-[80px] w-full rounded-md border border-border-default bg-background px-3 py-2 text-sm shadow-sm placeholder:text-muted-foreground focus:outline-none focus:ring-2 focus:ring-blue-500/20 dark:focus:ring-blue-400/20 disabled:cursor-not-allowed disabled:opacity-50",
           className,
         )}
         ref={ref}