feat(cms,asset): add comprehensive test suite and finalize modules

- Add comprehensive test suite for CMS and Asset modules using Pest Framework
- Implement ContentTypeService::delete() protection against deletion of in-use content types
- Add CannotDeleteContentTypeInUseException for better error handling
- Fix DerivatPipelineRegistry::getAllPipelines() to handle object uniqueness correctly
- Fix VariantName::getScale() to correctly parse scales with file extensions
- Update CMS module documentation with new features, exceptions, and test coverage
- Add CmsTestHelpers and AssetTestHelpers for test data factories
- Fix BlockTypeRegistry to be immutable after construction
- Update ContentTypeService to check for associated content before deletion
- Improve BlockRendererRegistry initialization

Test coverage:
- Value Objects: All CMS and Asset value objects
- Services: ContentService, ContentTypeService, SlugGenerator, BlockValidator, ContentLocalizationService, AssetService, DeduplicationService, MetadataExtractor
- Repositories: All database repositories with mocked connections
- Rendering: Block renderers and ContentRenderer
- Controllers: API endpoints for both modules

254 tests passing, 38 remaining (mostly image processing pipeline tests)

tests/Unit/Domain/Cms/ValueObjects/ContentSlugTest.php

@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+use App\Domain\Cms\ValueObjects\ContentSlug;
+
+describe('ContentSlug', function () {
+    it('can be created from valid string', function () {
+        $slug = ContentSlug::fromString('my-awesome-page');
+
+        expect($slug->toString())->toBe('my-awesome-page');
+        expect((string) $slug)->toBe('my-awesome-page');
+    });
+
+    it('accepts lowercase letters, numbers, hyphens, and underscores', function () {
+        $validSlugs = ['page', 'blog-post', 'product_123', 'my-content-slug'];
+
+        foreach ($validSlugs as $slugStr) {
+            $slug = ContentSlug::fromString($slugStr);
+            expect($slug->toString())->toBe($slugStr);
+        }
+    });
+
+    it('throws exception for empty string', function () {
+        expect(fn () => ContentSlug::fromString(''))
+            ->toThrow(InvalidArgumentException::class, 'Content slug cannot be empty');
+    });
+
+    it('throws exception for uppercase letters', function () {
+        expect(fn () => ContentSlug::fromString('My-Page'))
+            ->toThrow(InvalidArgumentException::class, 'Content slug must contain only lowercase letters, numbers, hyphens, and underscores');
+    });
+
+    it('throws exception for spaces', function () {
+        expect(fn () => ContentSlug::fromString('my page'))
+            ->toThrow(InvalidArgumentException::class);
+    });
+
+    it('throws exception for special characters', function () {
+        expect(fn () => ContentSlug::fromString('my@page'))
+            ->toThrow(InvalidArgumentException::class);
+    });
+
+    it('can compare two ContentSlugs for equality', function () {
+        $slug1 = ContentSlug::fromString('my-page');
+        $slug2 = ContentSlug::fromString('my-page');
+        $slug3 = ContentSlug::fromString('other-page');
+
+        expect($slug1->equals($slug2))->toBeTrue();
+        expect($slug1->equals($slug3))->toBeFalse();
+    });
+});
+