feat: Add Camera Settings dialog for UVC controls and Qt parameters

- Implemented CameraSettingsDialog to manage UVC and Qt camera controls.
- Integrated UVC parameter sliders and auto controls for brightness, contrast, saturation, hue, sharpness, gamma, white balance, backlight compensation, and exposure.
- Added functionality to change white balance and exposure settings via Qt controls.
- Updated MainWindow to open CameraSettingsDialog and manage UVC controller lifecycle.
- Enhanced AppMenuBar to include a Camera Settings option.
- Created tests for UVC controller abstraction layer and parameter info.
- Documented camera specifications and supported features in new markdown files.

app/camera/uvc/stub.py

@@ -0,0 +1,43 @@
+"""Null (no-op) UVC controller — used when no native library is available."""
+
+from __future__ import annotations
+
+import logging
+
+from app.camera.uvc.base import UvcControllerBase, UvcParam, UvcParamInfo
+
+logger = logging.getLogger(__name__)
+
+
+class NullUvcController(UvcControllerBase):
+    """
+    Fallback controller that reports all controls as unsupported.
+
+    Used on platforms where no UVC library is installed or when device
+    enumeration fails.
+    """
+
+    def open(self, device_name: str) -> bool:  # noqa: ARG002
+        return False
+
+    def close(self) -> None:
+        pass
+
+    def is_open(self) -> bool:
+        return False
+
+    def get_param_info(self, param: UvcParam) -> UvcParamInfo:
+        return UvcParamInfo(param=param, supported=False)
+
+    def get_all_params(self) -> list[UvcParamInfo]:
+        return [UvcParamInfo(param=p, supported=False) for p in UvcParam]
+
+    def set_value(self, param: UvcParam, value: int) -> bool:  # noqa: ARG002
+        logger.debug("NullUvcController: set_value ignored (%s=%d)", param.name, value)
+        return False
+
+    def set_auto(self, param: UvcParam, enabled: bool) -> bool:  # noqa: ARG002
+        logger.debug(
+            "NullUvcController: set_auto ignored (%s, auto=%s)", param.name, enabled
+        )
+        return False