feat: Add video playback functionality and inference support

- Introduced VideoPlayer class to handle local video playback, emitting frames via frame_ready signal.
- Updated MainWindow to switch between camera and video sources, integrating video playback controls.
- Enhanced AppMenuBar with options to open video files and manage inference models.
- Implemented BboxOverlay for displaying detection results on video frames.
- Added InferenceManager to manage YOLO inference in a separate process, with error handling and restart logic.
- Created tests for BboxOverlay and InferenceManager to ensure functionality and robustness.
- Updated pyproject.toml to include optional dependencies for inference support.

pyproject.toml

@@ -8,6 +8,14 @@ dependencies = [
     "psutil>=6.0",
 ]
 
+[project.optional-dependencies]
+# Install inference support: pip install -e ".[inference]"
+# or: pip install ultralytics numpy
+inference = [
+    "ultralytics>=8.0",
+    "numpy>=1.24",
+]
+
 [project.scripts]
 duck-preview = "app.main:main"