Allow setting the Ping360 scan direction

We already have a mount offset (per #256) that specifies the physical rotation of the sonar device, but it would also be useful to have a control for which direction to scan that's intended for adjustment while operating.

1. It should allow the user to specify which direction sector scanning should focus on (e.g. you could be maintaining a distance from a jetty on the right, and decide to do a sector scan only on the right side).
2. It should visually show which way the sector is pointing (relative to the vehicle, or relative to cardinal directions (e.g. North) if doing heading compensation).
3. It would be nice if a menu interface for it would be on a circle rather than a slider, but even better if it's possible to just directly drag the outside of a sector scan to point in the desired direction.

Start by locating the existing mount-offset and sector-scan controls referenced in the issue; no files, tests, or entry points are named. Review how Ping360 direction is represented, then clarify the interaction and heading-compensation expectations before implementation. Done should cover choosing a scan direction, showing its orientation, and supporting the agreed control style.

Written by the indexing model from the issue text.