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/Services/LLM/Providers/AbstractProvider.php

@@ -0,0 +1,103 @@
+<?php
+
+namespace App\Services\LLM\Providers;
+
+use App\Services\LLM\Contracts\ProviderInterface;
+use App\Exceptions\ProviderException;
+use Illuminate\Support\Facades\Http;
+use Illuminate\Support\Facades\Log;
+
+abstract class AbstractProvider implements ProviderInterface
+{
+    protected string $apiKey;
+    protected string $baseUrl;
+    protected int $timeout = 60;
+    protected int $retryAttempts = 3;
+    protected int $retryDelay = 1000; // milliseconds
+
+    public function __construct(string $apiKey)
+    {
+        $this->apiKey = $apiKey;
+    }
+
+    /**
+     * Build request payload for provider
+     */
+    abstract protected function buildRequest(array $messages, array $options): array;
+
+    /**
+     * Get authorization headers for provider
+     */
+    abstract protected function getAuthHeaders(): array;
+
+    /**
+     * Make HTTP request with retry logic
+     */
+    protected function makeRequest(string $endpoint, array $data): array
+    {
+        $attempt = 0;
+        $lastException = null;
+
+        while ($attempt < $this->retryAttempts) {
+            try {
+                $response = Http::withHeaders($this->getAuthHeaders())
+                    ->timeout($this->timeout)
+                    ->post($this->baseUrl . $endpoint, $data);
+
+                if ($response->successful()) {
+                    return $response->json();
+                }
+
+                // Handle specific HTTP errors
+                if ($response->status() === 401) {
+                    throw new ProviderException('Invalid API key', 401);
+                }
+
+                if ($response->status() === 429) {
+                    throw new ProviderException('Rate limit exceeded', 429);
+                }
+
+                if ($response->status() >= 500) {
+                    throw new ProviderException('Provider server error', $response->status());
+                }
+
+                throw new ProviderException(
+                    'Request failed: ' . $response->body(),
+                    $response->status()
+                );
+
+            } catch (\Exception $e) {
+                $lastException = $e;
+                $attempt++;
+
+                if ($attempt < $this->retryAttempts) {
+                    Log::warning("Provider request failed, retrying ({$attempt}/{$this->retryAttempts})", [
+                        'provider' => static::class,
+                        'error' => $e->getMessage()
+                    ]);
+                    usleep($this->retryDelay * 1000);
+                }
+            }
+        }
+
+        throw new ProviderException(
+            'All retry attempts failed: ' . ($lastException ? $lastException->getMessage() : 'Unknown error'),
+            $lastException ? $lastException->getCode() : 500
+        );
+    }
+
+    /**
+     * Validate API key by making a test request
+     */
+    public function validateApiKey(): bool
+    {
+        try {
+            $this->chatCompletion([
+                ['role' => 'user', 'content' => 'test']
+            ], ['max_tokens' => 5]);
+            return true;
+        } catch (\Exception $e) {
+            return false;
+        }
+    }
+}