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/src/wled_controller/main.py

@@ -23,7 +23,6 @@ from wled_controller.core.processing.processor_manager import (
 from wled_controller.storage import DeviceStore
 from wled_controller.storage.template_store import TemplateStore
 from wled_controller.storage.postprocessing_template_store import PostprocessingTemplateStore
-from wled_controller.storage.pattern_template_store import PatternTemplateStore
 from wled_controller.storage.picture_source_store import PictureSourceStore
 from wled_controller.storage.output_target_store import OutputTargetStore
 from wled_controller.storage.color_strip_store import ColorStripStore
@@ -77,7 +76,6 @@ template_store = TemplateStore(db)
 pp_template_store = PostprocessingTemplateStore(db)
 picture_source_store = PictureSourceStore(db)
 output_target_store = OutputTargetStore(db)
-pattern_template_store = PatternTemplateStore(db)
 color_strip_store = ColorStripStore(db)
 audio_source_store = AudioSourceStore(db)
 audio_template_store = AudioTemplateStore(db)
@@ -105,7 +103,6 @@ processor_manager = ProcessorManager(
         picture_source_store=picture_source_store,
         capture_template_store=template_store,
         pp_template_store=pp_template_store,
-        pattern_template_store=pattern_template_store,
         device_store=device_store,
         color_strip_store=color_strip_store,
         audio_source_store=audio_source_store,
@@ -195,7 +192,6 @@ async def lifespan(app: FastAPI):
         processor_manager,
         database=db,
         pp_template_store=pp_template_store,
-        pattern_template_store=pattern_template_store,
         picture_source_store=picture_source_store,
         output_target_store=output_target_store,
         color_strip_store=color_strip_store,
@@ -237,6 +233,7 @@ async def lifespan(app: FastAPI):
 
     logger.info(f"Registered {len(devices)} devices for health monitoring")
 
+    # Migrate KC targets → key_colors CSS sources
     # Register output targets in processor manager
     targets = output_target_store.get_all_targets()
     registered_targets = 0