Add WREN_DRY_RUN environment variable for safe testing

Prevent accidental creation of real carbon offsets during development:
- Add WREN_DRY_RUN environment variable (default: true for dev)
- Update webhook fulfillment to use env variable instead of hardcoded value
- Log warning when in dry run mode for visibility
- Production deployments should set WREN_DRY_RUN=false

This allows safe testing with Stripe test cards without creating real Wren offset orders.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

server/.env.example

@@ -4,6 +4,8 @@ STRIPE_WEBHOOK_SECRET=whsec_your_webhook_secret_here
 
 # Wren Climate API
 WREN_API_TOKEN=35c025d9-5dbb-404b-85aa-19b09da0578d
+# Set to 'true' for testing (no real offsets created), 'false' for production
+WREN_DRY_RUN=true
 
 # Server Configuration
 PORT=3001

server/routes/webhooks.js

@@ -144,6 +144,13 @@ async function fulfillOrder(order, session) {
   try {
     console.log(`🌱 Fulfilling order ${order.id} via Wren API...`);
 
+    // Determine if we should use dry run mode based on environment
+    const isDryRun = process.env.WREN_DRY_RUN === 'true';
+
+    if (isDryRun) {
+      console.log('⚠️  DRY RUN MODE: No real offset will be created');
+    }
+
     // Create Wren offset order
     const wrenOrder = await createWrenOffsetOrder({
       tons: order.tons,
@@ -151,7 +158,7 @@ async function fulfillOrder(order, session) {
       customerEmail: session.customer_details?.email || order.customer_email,
       currency: order.currency,
       amountCents: order.total_amount,
-      dryRun: false, // Set to true for testing without creating real offsets
+      dryRun: isDryRun,
     });
 
     // Update order with Wren order ID