fix(web): onboarding — locale-aware end date, dynamic plan, completion event

- End date no longer hard-codes tr-TR; follows the active locale.
- The plan badge reads from subscription.plan.key (falls back to "full"),
  so a future change to what the trial provisions doesn't make the UI lie.
- The "Şase Aramaya Başla" CTA captures onboarding_completed, so the
  funnel can distinguish a user who actually clicked through vs one who
  dismissed.

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

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

@@ -57,7 +57,7 @@ export function WelcomeOnboardingModal({
   refCode: string | null;
   onFinished: () => void;
 }) {
-  const { t } = useTranslation();
+  const { t, locale } = useTranslation();
   const queryClient = useQueryClient();
   const [phase, setPhase] = useState<"provisioning" | "completed">("provisioning");
   const [animationEnded, setAnimationEnded] = useState(false);
@@ -269,7 +269,7 @@ export function WelcomeOnboardingModal({
                   {t("subscription.currentPlan")}
                 </span>
                 <Badge className="bg-brand text-brand-foreground">
-                  {t("subscription.plans.full.name")}
+                  {t(`subscription.plans.${subscription?.plan?.key ?? "full"}.name`)}
                 </Badge>
               </div>
               <div className="flex items-center justify-between">
@@ -286,7 +286,9 @@ export function WelcomeOnboardingModal({
                     {t("subscription.endDate")}
                   </span>
                   <span className="text-sm font-medium leading-5">
-                    {new Date(subscription.endDate).toLocaleDateString("tr-TR")}
+                    {new Date(subscription.endDate).toLocaleDateString(
+                      locale === "tr" ? "tr-TR" : "en-US",
+                    )}
                   </span>
                 </div>
               )}
@@ -303,7 +305,10 @@ export function WelcomeOnboardingModal({
             <Button
               size="lg"
               className="bg-brand text-brand-foreground hover:bg-brand/90"
-              onClick={onFinished}
+              onClick={() => {
+                capture("onboarding_completed", { source: "welcome_onboarding" });
+                onFinished();
+              }}
             >
               {t("subscription.onboarding.startSearching")}
               <ArrowRight className="ml-2 h-4 w-4" />