fix(test): guard Stripe init in skipped bonus-flow spec

The describe.skipIf callback body still runs at collection time, so
new Stripe(stripeKey!) threw in CI where STRIPE_SECRET_KEY is unset.
Construct the client only when a test key is present.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: steebchen

apps/api/src/routes/end-user-bonus-flow.spec.ts

@@ -41,7 +41,9 @@ interface AdminMetrics {
 describe.skipIf(!hasStripeTestKey)(
 	"end-user bonus full flow (real Stripe)",
 	() => {
-		const stripe = new Stripe(stripeKey!);
+		const stripe = hasStripeTestKey
+			? new Stripe(stripeKey!)
+			: (undefined as unknown as Stripe);
 		let adminCookie: string;
 
 		beforeEach(async () => {