fix(web): onboarding micro-polish — autofocus CTA, swap hard-coded red token

- Auto-focus the "Şase Aramaya Başla" button when the completed card
  mounts so keyboard users can Enter through without tabbing.
- Replace the hard-coded `text-red-600 dark:text-red-400` on the trial
  error message with the `text-destructive` design token.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/components/onboarding/welcome-onboarding-modal.tsx

@@ -67,6 +67,7 @@ export function WelcomeOnboardingModal({
   const [escapeHatchEnabled, setEscapeHatchEnabled] = useState(false);
   const provisionedRef = useRef(false);
   const refAppliedRef = useRef(false);
+  const completeCtaRef = useRef<HTMLButtonElement>(null);
   const MAX_FAILURES = 2;
   const STUCK_TIMEOUT_MS = 30_000;
   const [isDark] = useState(() => {
@@ -161,6 +162,16 @@ export function WelcomeOnboardingModal({
     });
   }, [phase, animationEnded, trialMutation.isSuccess, queryClient]);
 
+  // Auto-focus the primary CTA when the completed card appears so keyboard
+  // users can confirm with Enter without having to tab through the card.
+  useEffect(() => {
+    if (phase === "completed") {
+      // Wait a tick so the element is in the DOM and Radix's focus trap has
+      // already moved focus into the dialog.
+      requestAnimationFrame(() => completeCtaRef.current?.focus());
+    }
+  }, [phase]);
+
   return (
     <Dialog
       open
@@ -240,7 +251,7 @@ export function WelcomeOnboardingModal({
             )}
             {trialMutation.isError && !escapeHatchEnabled && (
               <div className="flex flex-col items-center gap-3">
-                <p className="text-sm leading-5 text-red-600 dark:text-red-400">
+                <p className="text-sm leading-5 text-destructive">
                   {t("subscription.onboarding.error")}
                 </p>
                 <Button variant="outline" onClick={() => trialMutation.mutate()}>
@@ -332,6 +343,7 @@ export function WelcomeOnboardingModal({
               </ul>
             </div>
             <Button
+              ref={completeCtaRef}
               size="lg"
               className="bg-brand text-brand-foreground hover:bg-brand/90"
               onClick={() => {