chore(pipeline): improve pipeline architecture

- Add capability-based dependency resolution with prefix matching
- Add EffectPluginStage with sensor binding support
- Add CameraStage adapter for camera integration
- Add DisplayStage adapter for display integration
- Add Pipeline metrics collection
- Add deprecation notices to legacy modules
- Update app.py with pipeline integration

engine/scroll.py

@@ -1,6 +1,11 @@
 """
 Render engine — ticker content, scroll motion, message panel, and firehose overlay.
 Orchestrates viewport, frame timing, and layers.
+
+.. deprecated::
+    This module contains legacy rendering/orchestration code. New pipeline code should
+    use the Stage-based pipeline architecture instead. This module is
+    maintained for backwards compatibility with the demo mode.
 """
 
 import random