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/Models/UserProviderCredential.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Support\Facades\Crypt;
+
+class UserProviderCredential extends Model
+{
+    protected $fillable = [
+        'user_id',
+        'provider',
+        'api_key',
+        'organization_id',
+        'is_active',
+        'last_used_at',
+    ];
+
+    protected $hidden = [
+        'api_key',
+    ];
+
+    protected $casts = [
+        'is_active' => 'boolean',
+        'last_used_at' => 'datetime',
+    ];
+
+    // Automatic encryption when setting
+    public function setApiKeyAttribute($value): void
+    {
+        $this->attributes['api_key'] = Crypt::encryptString($value);
+    }
+
+    // Automatic decryption when getting
+    public function getApiKeyAttribute($value): string
+    {
+        return Crypt::decryptString($value);
+    }
+
+    public function user(): BelongsTo
+    {
+        return $this->belongsTo(User::class);
+    }
+
+    public function markAsUsed(): void
+    {
+        $this->update(['last_used_at' => now()]);
+    }
+}