Add Pattern Templates for Key Colors targets with visual canvas editor

Introduce Pattern Template entity as a reusable rectangle layout that
Key Colors targets reference via pattern_template_id. This replaces
inline rectangle storage with a shared template system.

Backend:
- New PatternTemplate data model, store (JSON persistence), CRUD API
- KC targets now reference pattern_template_id instead of inline rectangles
- ProcessorManager resolves pattern template at KC processing start
- Picture source test endpoint supports capture_duration=0 for single frame
- Delete protection: 409 when template is referenced by a KC target

Frontend:
- Pattern Templates section in Key Colors sub-tab with card UI
- Visual canvas editor with drag-to-move, 8-point resize handles
- Background capture from any picture source for visual alignment
- Precise coordinate list synced bidirectionally with canvas
- Resizable editor container, viewport-constrained modal
- KC target editor uses pattern template dropdown instead of inline rects
- Localization (en/ru) for all new UI elements

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/api/dependencies.py

@@ -4,6 +4,7 @@ from wled_controller.core.processor_manager import ProcessorManager
 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.picture_target_store import PictureTargetStore
 
@@ -11,6 +12,7 @@ from wled_controller.storage.picture_target_store import PictureTargetStore
 _device_store: DeviceStore | None = None
 _template_store: TemplateStore | None = None
 _pp_template_store: PostprocessingTemplateStore | None = None
+_pattern_template_store: PatternTemplateStore | None = None
 _picture_source_store: PictureSourceStore | None = None
 _picture_target_store: PictureTargetStore | None = None
 _processor_manager: ProcessorManager | None = None
@@ -37,6 +39,13 @@ def get_pp_template_store() -> PostprocessingTemplateStore:
     return _pp_template_store
 
 
+def get_pattern_template_store() -> PatternTemplateStore:
+    """Get pattern template store dependency."""
+    if _pattern_template_store is None:
+        raise RuntimeError("Pattern template store not initialized")
+    return _pattern_template_store
+
+
 def get_picture_source_store() -> PictureSourceStore:
     """Get picture source store dependency."""
     if _picture_source_store is None:
@@ -63,15 +72,17 @@ def init_dependencies(
     template_store: TemplateStore,
     processor_manager: ProcessorManager,
     pp_template_store: PostprocessingTemplateStore | None = None,
+    pattern_template_store: PatternTemplateStore | None = None,
     picture_source_store: PictureSourceStore | None = None,
     picture_target_store: PictureTargetStore | None = None,
 ):
     """Initialize global dependencies."""
     global _device_store, _template_store, _processor_manager
-    global _pp_template_store, _picture_source_store, _picture_target_store
+    global _pp_template_store, _pattern_template_store, _picture_source_store, _picture_target_store
     _device_store = device_store
     _template_store = template_store
     _processor_manager = processor_manager
     _pp_template_store = pp_template_store
+    _pattern_template_store = pattern_template_store
     _picture_source_store = picture_source_store
     _picture_target_store = picture_target_store