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/tests/Unit/Services/MistralProviderTest.php

@@ -0,0 +1,128 @@
+<?php
+
+namespace Tests\Unit\Services;
+
+use Tests\TestCase;
+use App\Services\LLM\Providers\MistralProvider;
+use App\Models\ModelPricing;
+use Illuminate\Support\Facades\Http;
+use Illuminate\Support\Facades\Cache;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+
+class MistralProviderTest extends TestCase
+{
+    use RefreshDatabase;
+
+    private MistralProvider $provider;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->provider = new MistralProvider('test-api-key');
+    }
+
+    public function test_builds_request_correctly(): void
+    {
+        $messages = [
+            ['role' => 'user', 'content' => 'Hello']
+        ];
+        
+        $options = [
+            'model' => 'mistral-small-latest',
+            'temperature' => 0.8,
+            'max_tokens' => 1000
+        ];
+
+        $reflection = new \ReflectionClass($this->provider);
+        $method = $reflection->getMethod('buildRequest');
+        $method->setAccessible(true);
+
+        $result = $method->invoke($this->provider, $messages, $options);
+
+        $this->assertEquals('mistral-small-latest', $result['model']);
+        $this->assertEquals(0.8, $result['temperature']);
+        $this->assertEquals(1000, $result['max_tokens']);
+        $this->assertEquals($messages, $result['messages']);
+        $this->assertArrayNotHasKey('stream', $result); // stream=false is filtered out
+    }
+
+    public function test_normalizes_response_correctly(): void
+    {
+        $rawResponse = [
+            'id' => 'cmpl-123',
+            'model' => 'mistral-small-latest',
+            'choices' => [
+                [
+                    'message' => [
+                        'role' => 'assistant',
+                        'content' => 'Bonjour! Comment puis-je vous aider?'
+                    ],
+                    'finish_reason' => 'stop'
+                ]
+            ],
+            'usage' => [
+                'prompt_tokens' => 12,
+                'completion_tokens' => 18,
+                'total_tokens' => 30
+            ]
+        ];
+
+        $normalized = $this->provider->normalizeResponse($rawResponse);
+
+        $this->assertEquals('cmpl-123', $normalized['id']);
+        $this->assertEquals('mistral-small-latest', $normalized['model']);
+        $this->assertEquals('Bonjour! Comment puis-je vous aider?', $normalized['content']);
+        $this->assertEquals('assistant', $normalized['role']);
+        $this->assertEquals('stop', $normalized['finish_reason']);
+        $this->assertEquals(12, $normalized['usage']['prompt_tokens']);
+        $this->assertEquals(18, $normalized['usage']['completion_tokens']);
+        $this->assertEquals(30, $normalized['usage']['total_tokens']);
+    }
+
+    public function test_calculates_cost_correctly(): void
+    {
+        ModelPricing::updateOrCreate(
+            [
+                'provider' => 'mistral',
+                'model' => 'mistral-small-latest',
+                'effective_from' => now()->toDateString(),
+            ],
+            [
+                'input_price_per_million' => 0.20,
+                'output_price_per_million' => 0.60,
+                'is_active' => true,
+            ]
+        );
+
+        Cache::flush();
+
+        $cost = $this->provider->calculateCost(1000, 500, 'mistral-small-latest');
+
+        // Expected: (1000/1M * 0.20) + (500/1M * 0.60) = 0.0002 + 0.0003 = 0.0005
+        $this->assertEquals(0.0005, $cost);
+    }
+
+    public function test_handles_api_errors(): void
+    {
+        Http::fake([
+            'https://api.mistral.ai/*' => Http::response(['error' => 'Invalid API key'], 401)
+        ]);
+
+        $this->expectException(\App\Exceptions\ProviderException::class);
+        $this->expectExceptionMessage('Invalid API key');
+
+        $this->provider->chatCompletion([
+            ['role' => 'user', 'content' => 'test']
+        ]);
+    }
+
+    public function test_get_supported_models(): void
+    {
+        $models = $this->provider->getSupportedModels();
+
+        $this->assertIsArray($models);
+        $this->assertContains('mistral-large-latest', $models);
+        $this->assertContains('mistral-small-latest', $models);
+        $this->assertContains('open-mixtral-8x7b', $models);
+    }
+}