refactor: key colors targets → CSS source type, HA target improvements

Key Colors refactor:
- New `key_colors` CSS source type with inline rectangles
- KeyColorsColorStripStream: extracts N colors from screen regions
- CSS editor: EntitySelect for picture source, IconSelect for color mode
- Configure Regions button on card opens pattern canvas editor
- Live WS preview at 5 FPS with rectangle overlay + color swatches
- Removed KC target type, pattern template entity, and related API routes
- Removed KC/pattern template sections from Targets tab

HA light target improvements:
- Update rate, transition, mappings, brightness VS now editable via PUT
- Card crosslinks for HA source, CSS source, brightness VS
- HA connection status icon, text metrics (Hz, uptime)
- Brightness value source selector in editor

server/tests/test_processor_manager.py

@@ -2,7 +2,10 @@
 
 import pytest
 
-from wled_controller.core.processing.processor_manager import ProcessorDependencies, ProcessorManager
+from wled_controller.core.processing.processor_manager import (
+    ProcessorDependencies,
+    ProcessorManager,
+)
 
 
 @pytest.fixture
@@ -230,8 +233,6 @@ def test_get_target_metrics(processor_manager):
 
 def test_target_type_detection(processor_manager):
     """Test target type detection via processor instances."""
-    from wled_controller.storage.key_colors_output_target import KeyColorsSettings
-    from wled_controller.core.processing.kc_target_processor import KCTargetProcessor
     from wled_controller.core.processing.wled_target_processor import WledTargetProcessor
 
     processor_manager.add_device(
@@ -245,13 +246,6 @@ def test_target_type_detection(processor_manager):
         device_id="test_device",
     )
 
-    processor_manager.add_kc_target(
-        target_id="kc_target",
-        picture_source_id="src_1",
-        settings=KeyColorsSettings(),
-    )
-
-    assert isinstance(processor_manager._processors["kc_target"], KCTargetProcessor)
     assert isinstance(processor_manager._processors["wled_target"], WledTargetProcessor)