Refactor capture engine architecture, rename PictureStream to PictureSource, and split API modules

- Separate CaptureEngine into stateless factory + stateful CaptureStream session
- Add LiveStream/LiveStreamManager for shared capture with reference counting
- Rename PictureStream to PictureSource across storage, API, and UI
- Remove legacy migration logic and unused compatibility code
- Split monolithic routes.py (1935 lines) into 5 focused route modules
- Split schemas.py (480 lines) into 7 schema modules with re-exports
- Extract dependency injection into dedicated dependencies.py

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

server/src/wled_controller/core/calibration.py

@@ -349,9 +349,6 @@ def create_default_calibration(led_count: int) -> CalibrationConfig:
 def calibration_from_dict(data: dict) -> CalibrationConfig:
     """Create calibration configuration from dictionary.
 
-    Supports both new format (leds_top/right/bottom/left) and legacy format
-    (segments list) for backward compatibility.
-
     Args:
         data: Dictionary with calibration data