feat: Add ModelsLab provider for image generation

[adhikjoshi]

Summary

Adds ModelsLab as a new image generation provider in Prism — a unified AI interface for Laravel.

What this PR adds

Provider class (src/Providers/ModelsLab/ModelsLab.php)

• Implements the images() method following the Provider interface
• Uses the standard Prism HTTP client pattern

Image handler (src/Providers/ModelsLab/Handlers/Images.php)

• Handles text-to-image generation via ModelsLab REST API
• Supports: Flux, SDXL, Realistic Vision, DreamShaper, Anything, and community models
• API key in request body (ModelsLab uses "key": "api_key", not Bearer token)

Configuration (config/prism.php)

'modelslab' => [
    'api_key' => env('MODELSLAB_API_KEY', ''),
    => env('MODELSLAB_URL', 'https:// 'url'modelslab.com/api/v6'),
],

Usage

use Prism\Prism\Facades\Prism;

// Using the facade
\$image = Prism::images()
    ->using('modelslab', [api_key => 'your-key'])
    ->generate('A sunset over mountains in watercolor style');

// Or via config
// Set MODELSLAB_API_KEY in .env, then:
\$image = Prism::images()
    ->using('modelslab')
    ->generate('A sunset over mountains');

Supported provider options

• width (default: 1024)
• height (default: 1024)
• samples (default: 1)
• num_inference_steps (default: 30)
• guidance_scale (default: 7.5)
• negative_prompt
• seed
• safety_checker (default: "no")

API Reference

• ModelsLab text-to-image docs
• Get API key