Change processing fee from 3% to 5%

Updated PROCESSING_FEE_PERCENT from 0.03 to 0.05 and updated the
line item description in Stripe checkout from "Processing Fee (3%)"
to "Processing Fee (5%)".

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

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

server/routes/checkout.js

@@ -12,7 +12,7 @@ const PORTFOLIO_PRICING = {
 };
 
 // Processing fee percentage
-const PROCESSING_FEE_PERCENT = 0.03; // 3%
+const PROCESSING_FEE_PERCENT = 0.05; // 5%
 
 /**
  * Calculate pricing with processing fee
@@ -81,7 +81,7 @@ router.post('/create-session', async (req, res) => {
         price_data: {
           currency: 'usd',
           product_data: {
-            name: 'Processing Fee (3%)',
+            name: 'Processing Fee (5%)',
             description: 'Transaction processing fee',
           },
           unit_amount: processingFee, // Processing fee in cents