Fix API controllers to use correct database column names

- Fix model_pricing table references (model_id -> model, display_name -> model)
- Fix price columns (output_price_per_1k -> output_price_per_million)
- Add price conversion (per_million / 1000 = per_1k) in all API responses
- Add whereNotNull('model') filters to exclude invalid entries
- Add getModelDisplayName() helper method to all controllers
- Fix AccountController to use gateway_users budget fields directly
- Remove Budget model dependencies from AccountController
- Add custom Scramble server URL configuration for API docs
- Create ScrambleServiceProvider to set correct /api prefix
- Add migration to rename user_id to gateway_user_id in llm_requests
- Add custom ApiGuard for gateway_users authentication
- Update all API controllers: AccountController, ModelController, PricingController, ProviderController

All API endpoints now working correctly:
- GET /api/account
- GET /api/models
- GET /api/pricing
- GET /api/providers/{provider}

laravel-app/resources/views/model-pricing/create.blade.php

@@ -187,7 +187,7 @@
             modelHint.textContent = 'Loading models from ' + provider + '...';
             
             try {
-                const response = await fetch(`/api/provider-models/${provider}`);
+                const response = await fetch(`/admin/provider-models/${provider}`);
                 const data = await response.json();
                 
                 if (data.success && data.models) {