debug: add logging to see checkout session params being sent to Stripe

Added console.log to debug Stripe 'resource_missing' error.

Will show: tier_level, tier_name, priceId, billingMode

Signed-off-by: Claude (Chronicler #57) <claude@firefrostgaming.com>

services/arbiter-3.0/src/routes/stripe.js

@@ -51,6 +51,13 @@ router.post('/create-checkout-session', cors(corsOptions), async (req, res) => {
     const priceId = product.stripe_price_id;
     const billingMode = product.billing_type === 'one-time' ? 'payment' : 'subscription';
     
+    console.log('🔍 Creating checkout session:', {
+      tier_level,
+      tier_name: product.tier_name,
+      priceId,
+      billingMode
+    });
+    
     // Create Stripe Checkout Session
     const sessionConfig = {
       payment_method_types: ['card'],