ROI: initialization and behavior

[biodotpe]

Summary

ROI-related controls are disabled on first launch, and its behavior is inconsistent with ROI settings.

Description

• On first launch of the web UI, Record ROI and Start Detection buttons are disabled.
• Buttons become enabled only after a ROI is manually defined in the GUI.
• Only Record ROI persists the selected ROI in the GUI.
• Snapshot saves images using the Display Resolution (Camera Config tab), not the ROI resolution.

Expected Behavior

• ROI-related controls should be usable on startup or initialize a default ROI.
• Snapshot behavior should be consistent with ROI settings or clearly documented.

Actual Behavior

• Controls are unusable until ROI is manually set.
• Snapshot ignores ROI resolution.