feat: integrate PHPStan, Rector and Pint code quality tools (#13)

* feat: integrate PHPStan, Rector and Pint code quality tools

- Add larastan, rector, and rector-laravel dev dependencies
- Configure PHPStan at max level with Larastan extension
- Configure Rector with Laravel sets and code quality rules
- Configure Pint with strict rules (final_class, strict_types)
- Add composer scripts: lint, test:lint, test:types, test:unit
- Add GitHub Actions workflow for CI on push/PR
- Apply code style fixes across all files

* docs: add code quality section to README

app/Http/Requests/Api/V1/LoginRequest.php

@@ -1,10 +1,17 @@
 <?php
 
+declare(strict_types=1);
+
 namespace App\Http\Requests\Api\V1;
 
+use Illuminate\Contracts\Validation\ValidationRule;
 use Illuminate\Foundation\Http\FormRequest;
 
-class LoginRequest extends FormRequest
+/**
+ * @property string $email
+ * @property string $password
+ */
+final class LoginRequest extends FormRequest
 {
     public function authorize(): bool
     {
@@ -12,7 +19,7 @@ class LoginRequest extends FormRequest
     }
 
     /**
-     * @return array<string, \Illuminate\Contracts\Validation\ValidationRule|array<mixed>|string>
+     * @return array<string, ValidationRule|array<mixed>|string>
      */
     public function rules(): array
     {

app/Http/Requests/Api/V1/RegisterRequest.php

@@ -1,10 +1,18 @@
 <?php
 
+declare(strict_types=1);
+
 namespace App\Http\Requests\Api\V1;
 
+use Illuminate\Contracts\Validation\ValidationRule;
 use Illuminate\Foundation\Http\FormRequest;
 
-class RegisterRequest extends FormRequest
+/**
+ * @property string $name
+ * @property string $email
+ * @property string $password
+ */
+final class RegisterRequest extends FormRequest
 {
     public function authorize(): bool
     {
@@ -12,7 +20,7 @@ class RegisterRequest extends FormRequest
     }
 
     /**
-     * @return array<string, \Illuminate\Contracts\Validation\ValidationRule|array<mixed>|string>
+     * @return array<string, ValidationRule|array<mixed>|string>
      */
     public function rules(): array
     {