Remove PayPal, simplify to QRIS-only with in-app QR display

- Remove PayPal payment option from checkout
- Add qr_string and qr_expires_at columns to orders table
- Update create-payment to store QR string in database
- Update pakasir-webhook to clear QR string after payment
- Simplify Checkout to redirect to order detail page
- Clean up unused imports and components

Flow:
1. User checks out with QRIS (only option)
2. Order created with payment_method='qris'
3. QR string stored in database
4. User redirected to Order Detail page
5. QR code displayed in-app with polling
6. After payment, QR string cleared, access granted

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

supabase/functions/pakasir-webhook/index.ts

@@ -95,6 +95,9 @@ serve(async (req) => {
         payment_provider: "pakasir",
         payment_method: payload.payment_method || "unknown",
         updated_at: new Date().toISOString(),
+        // Clear QR string after payment
+        qr_string: null,
+        qr_expires_at: null,
       })
       .eq("id", order.id);