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/Asset/Services/MetadataExtractorTest.php

@@ -0,0 +1,86 @@
+<?php
+
+declare(strict_types=1);
+
+use App\Domain\Asset\Services\MetadataExtractor;
+
+describe('MetadataExtractor', function () {
+    beforeEach(function () {
+        $this->extractor = new MetadataExtractor();
+    });
+
+    it('extracts image dimensions from valid image', function () {
+        // Create a minimal valid JPEG (1x1 pixel)
+        $imageContent = "\xFF\xD8\xFF\xE0\x00\x10JFIF\x00\x01\x01\x01\x00H\x00H\x00\x00\xFF\xD9";
+        
+        // Create a real 1x1 pixel image using GD
+        $img = imagecreatetruecolor(100, 200);
+        ob_start();
+        imagejpeg($img);
+        $imageContent = ob_get_clean();
+        imagedestroy($img);
+
+        $meta = $this->extractor->extractImageMetadata($imageContent);
+
+        expect($meta->getWidth())->toBe(100);
+        expect($meta->getHeight())->toBe(200);
+    });
+
+    it('returns empty metadata for invalid image content', function () {
+        $meta = $this->extractor->extractImageMetadata('invalid-image-content');
+
+        expect($meta->getWidth())->toBeNull();
+        expect($meta->getHeight())->toBeNull();
+    });
+
+    it('extracts EXIF data when available', function () {
+        // Create a minimal JPEG
+        $img = imagecreatetruecolor(100, 100);
+        ob_start();
+        imagejpeg($img);
+        $imageContent = ob_get_clean();
+        imagedestroy($img);
+
+        $meta = $this->extractor->extractImageMetadata($imageContent);
+
+        // EXIF might not be available in test environment, but method should not throw
+        expect($meta)->toBeInstanceOf(\App\Domain\Asset\ValueObjects\AssetMetadata::class);
+    });
+
+    it('returns empty metadata for video content', function () {
+        $meta = $this->extractor->extractVideoMetadata('video-content');
+
+        expect($meta->toArray())->toBe([]);
+    });
+
+    it('returns empty metadata for audio content', function () {
+        $meta = $this->extractor->extractAudioMetadata('audio-content');
+
+        expect($meta->toArray())->toBe([]);
+    });
+
+    it('returns null for blurhash generation', function () {
+        $img = imagecreatetruecolor(100, 100);
+        ob_start();
+        imagejpeg($img);
+        $imageContent = ob_get_clean();
+        imagedestroy($img);
+
+        $blurhash = $this->extractor->generateBlurhash($imageContent);
+
+        expect($blurhash)->toBeNull();
+    });
+
+    it('returns null for dominant color extraction', function () {
+        $img = imagecreatetruecolor(100, 100);
+        ob_start();
+        imagejpeg($img);
+        $imageContent = ob_get_clean();
+        imagedestroy($img);
+
+        $color = $this->extractor->extractDominantColor($imageContent);
+
+        expect($color)->toBeNull();
+    });
+});
+