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/Contracts/ProviderInterface.php

@@ -0,0 +1,48 @@
+<?php
+
+namespace App\Services\LLM\Contracts;
+
+interface ProviderInterface
+{
+    /**
+     * Send a chat completion request to the provider
+     *
+     * @param array $messages Array of message objects with 'role' and 'content'
+     * @param array $options Additional options (model, temperature, max_tokens, etc.)
+     * @return array Raw provider response
+     * @throws \App\Exceptions\ProviderException
+     */
+    public function chatCompletion(array $messages, array $options = []): array;
+
+    /**
+     * Normalize provider response to common format
+     *
+     * @param array $response Raw provider response
+     * @return array Normalized response with: id, model, content, usage, finish_reason
+     */
+    public function normalizeResponse(array $response): array;
+
+    /**
+     * Calculate cost for given token usage
+     *
+     * @param int $promptTokens Number of prompt tokens
+     * @param int $completionTokens Number of completion tokens
+     * @param string $model Model name
+     * @return float Total cost in USD
+     */
+    public function calculateCost(int $promptTokens, int $completionTokens, string $model): float;
+
+    /**
+     * Get supported models for this provider
+     *
+     * @return array List of supported model names
+     */
+    public function getSupportedModels(): array;
+
+    /**
+     * Validate API key
+     *
+     * @return bool True if API key is valid
+     */
+    public function validateApiKey(): bool;
+}