Refactor: Align system with gateway_users architecture

- Fixed database relationships: LlmRequest now properly uses gateway_user_id instead of user_id
- Updated Models: GatewayUser and LlmRequest relationships corrected
- Removed User->llmRequests relationship (admin users don't have LLM requests)
- Simplified Dashboard: Now shows Gateway User statistics instead of admin users
- Removed obsolete Budgets management pages (budgets handled directly in gateway_users)
- Removed User Budgets admin section (redundant with gateway_users management)
- Fixed view errors: Added null-checks for user_id in keys views
- Updated navigation: Removed Budget and User Budget links
- Updated routes: Cleaned up unused BudgetController and UserManagementController routes
- Simplified StatisticsService: Focus on gateway_users and basic metrics only

laravel-app/resources/views/gateway-users/edit.blade.php

@@ -47,28 +47,6 @@
                     @enderror
                 </div>
 
-                <!-- Budget -->
-                <div class="mb-6">
-                    <label for="budget_id" class="block text-sm font-medium text-gray-700 mb-2">
-                        Budget Template
-                    </label>
-                    <select name="budget_id" 
-                            id="budget_id"
-                            class="block w-full rounded-md border-gray-300 shadow-sm focus:border-indigo-500 focus:ring-indigo-500 sm:text-sm @error('budget_id') border-red-300 @enderror">
-                        <option value="">No Budget</option>
-                        @foreach($budgets as $budget)
-                        <option value="{{ $budget->budget_id }}" 
-                                {{ old('budget_id', $user->budget_id) == $budget->budget_id ? 'selected' : '' }}>
-                            {{ $budget->budget_id }} - ${{ number_format($budget->max_budget, 2) }} 
-                            ({{ floor($budget->budget_duration_sec / 86400) }}d)
-                        </option>
-                        @endforeach
-                    </select>
-                    @error('budget_id')
-                    <p class="mt-1 text-sm text-red-600">{{ $message }}</p>
-                    @enderror
-                </div>
-
                 <!-- Current Spend (Read-only) -->
                 <div class="mb-6">
                     <label class="block text-sm font-medium text-gray-700 mb-2">