Introduce Picture Targets to separate processing from devices

Add PictureTarget entity that bridges PictureSource to output device,
separating processing settings from device connection/calibration state.
This enables future target types (Art-Net, E1.31) and cleanly decouples
"what to stream" from "where to stream."

- Add PictureTarget/WledPictureTarget dataclasses and storage
- Split ProcessorManager into DeviceState (health) + TargetState (processing)
- Add /api/v1/picture-targets endpoints (CRUD, start/stop, settings, metrics)
- Simplify device API (remove processing/settings/metrics endpoints)
- Auto-migrate existing device settings to picture targets on first startup
- Add Targets tab to WebUI with target cards and editor modal
- Add en/ru locale keys for targets UI

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

server/src/wled_controller/api/dependencies.py

@@ -5,12 +5,14 @@ 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.picture_source_store import PictureSourceStore
+from wled_controller.storage.picture_target_store import PictureTargetStore
 
 # Global instances (initialized in main.py)
 _device_store: DeviceStore | None = None
 _template_store: TemplateStore | None = None
 _pp_template_store: PostprocessingTemplateStore | None = None
 _picture_source_store: PictureSourceStore | None = None
+_picture_target_store: PictureTargetStore | None = None
 _processor_manager: ProcessorManager | None = None
 
 
@@ -42,6 +44,13 @@ def get_picture_source_store() -> PictureSourceStore:
     return _picture_source_store
 
 
+def get_picture_target_store() -> PictureTargetStore:
+    """Get picture target store dependency."""
+    if _picture_target_store is None:
+        raise RuntimeError("Picture target store not initialized")
+    return _picture_target_store
+
+
 def get_processor_manager() -> ProcessorManager:
     """Get processor manager dependency."""
     if _processor_manager is None:
@@ -55,11 +64,14 @@ def init_dependencies(
     processor_manager: ProcessorManager,
     pp_template_store: PostprocessingTemplateStore | None = None,
     picture_source_store: PictureSourceStore | None = None,
+    picture_target_store: PictureTargetStore | None = None,
 ):
     """Initialize global dependencies."""
-    global _device_store, _template_store, _processor_manager, _pp_template_store, _picture_source_store
+    global _device_store, _template_store, _processor_manager
+    global _pp_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
     _picture_source_store = picture_source_store
+    _picture_target_store = picture_target_store