security: Enhance production security and reliability

🔒 Security Enhancements:
- Add HTTPS validation for production URLs with comprehensive checks
- Implement type-safe Mollie status mapping to prevent type confusion
- Add robust request body handling with proper error boundaries

🚀 Reliability Improvements:
- Implement optimistic locking to prevent webhook race conditions
- Add providerId field indexing for efficient payment lookups
- Include webhook processing metadata for audit trails

📊 Performance Optimizations:
- Index providerId field for faster webhook payment queries
- Optimize concurrent webhook handling with version checking
- Add graceful degradation for update conflicts

🛡️ Production Readiness:
- Validate HTTPS protocol enforcement in production
- Prevent localhost URLs in production environments
- Enhanced error context and logging for debugging

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

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

src/collections/payments.ts

@@ -29,6 +29,7 @@ export function createPaymentsCollection(pluginConfig: BillingPluginConfig): Col
       },
       label: 'Provider Payment ID',
       unique: true,
+      index: true, // Ensure this field is indexed for webhook lookups
     },
     {
       name: 'status',