Add complete Laravel LLM Gateway implementation

Core Features:
- Multi-provider support (OpenAI, Anthropic, DeepSeek, Gemini, Mistral)
- Provider service architecture with abstract base class
- Dynamic model discovery from provider APIs
- Encrypted per-user provider credentials storage

Admin Interface:
- Complete admin panel with Livewire components
- User management with CRUD operations
- API key management with testing capabilities
- Budget system with limits and reset schedules
- Usage logs with filtering and CSV export
- Model pricing management with cost calculator
- Dashboard with Chart.js visualizations

Database Schema:
- MariaDB migrations for all tables
- User provider credentials (encrypted)
- LLM request logging
- Budget tracking and rate limiting
- Model pricing configuration

API Implementation:
- OpenAI-compatible endpoints
- Budget checking middleware
- Rate limit enforcement
- Request logging jobs
- Cost calculation service

Testing:
- Unit tests for all provider services
- Provider factory tests
- Cost calculator tests

Documentation:
- Admin user seeder
- Model pricing seeder
- Configuration files

laravel-app/app/Exceptions/InsufficientBudgetException.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace App\Exceptions;
+
+use Exception;
+
+class InsufficientBudgetException extends Exception
+{
+    protected $code = 402; // Payment Required
+
+    public function __construct(string $message = "Insufficient budget", int $code = 402, ?Exception $previous = null)
+    {
+        parent::__construct($message, $code, $previous);
+    }
+
+    /**
+     * Render the exception as an HTTP response.
+     */
+    public function render()
+    {
+        return response()->json([
+            'success' => false,
+            'error' => 'budget_exceeded',
+            'message' => $this->getMessage(),
+        ], $this->code);
+    }
+}

laravel-app/app/Exceptions/ProviderException.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Exceptions;
+
+use Exception;
+
+class ProviderException extends Exception
+{
+    public function __construct(string $message = "Provider error", int $code = 500, ?Exception $previous = null)
+    {
+        parent::__construct($message, $code, $previous);
+    }
+
+    /**
+     * Render the exception as an HTTP response.
+     */
+    public function render()
+    {
+        return response()->json([
+            'success' => false,
+            'error' => 'provider_error',
+            'message' => $this->getMessage(),
+        ], $this->code);
+    }
+}

laravel-app/app/Exceptions/RateLimitExceededException.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace App\Exceptions;
+
+use Exception;
+
+class RateLimitExceededException extends Exception
+{
+    protected $code = 429; // Too Many Requests
+
+    public function __construct(string $message = "Rate limit exceeded", int $code = 429, ?Exception $previous = null)
+    {
+        parent::__construct($message, $code, $previous);
+    }
+
+    /**
+     * Render the exception as an HTTP response.
+     */
+    public function render()
+    {
+        return response()->json([
+            'success' => false,
+            'error' => 'rate_limit_exceeded',
+            'message' => $this->getMessage(),
+        ], $this->code);
+    }
+}