feat: Add hybrid quality evaluation system with CLIP and VLM support

- Add FeatureExtractor for CLIP-based image/text feature extraction
- Add ObjectiveMetricsCalculator for technical quality metrics
- Add VLMEvaluator for vision language model evaluation
- Add HybridQualityGate combining objective + VLM evaluation
- Enhance CharacterMemory with visual feature support
- Add quality optional dependency (torch, ftfy, regex)
- Add unit tests for new modules

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/test_feature_extractor.py

@@ -0,0 +1,47 @@
+# Copyright (C) 2025 AIDC-AI
+# Tests for FeatureExtractor
+
+import pytest
+
+from pixelle_video.services.quality.feature_extractor import (
+    FeatureExtractor,
+    FeatureExtractorConfig,
+)
+
+
+class TestFeatureExtractorConfig:
+    """Tests for FeatureExtractorConfig"""
+
+    def test_default_values(self):
+        config = FeatureExtractorConfig()
+        assert config.model_name == "ViT-B/32"
+        assert config.device == "auto"
+        assert config.cache_features is True
+
+
+class TestFeatureExtractor:
+    """Tests for FeatureExtractor"""
+
+    def test_init_default(self):
+        extractor = FeatureExtractor()
+        assert extractor.config.model_name == "ViT-B/32"
+
+    def test_is_available_check(self):
+        """Test availability check (may be True or False)"""
+        extractor = FeatureExtractor()
+        # Just check it returns a boolean
+        assert isinstance(extractor.is_available, bool)
+
+    def test_extract_without_clip(self):
+        """Test graceful degradation when CLIP unavailable"""
+        extractor = FeatureExtractor()
+        if not extractor.is_available:
+            result = extractor.extract_image_features("/fake/path.png")
+            assert result is None
+
+    def test_clear_cache(self):
+        """Test cache clearing"""
+        extractor = FeatureExtractor()
+        extractor._feature_cache["test"] = "value"
+        extractor.clear_cache()
+        assert len(extractor._feature_cache) == 0