Zoom behavior and reset to home view

#### Issue details

The normal scroll zoom behavior in the flight and planning screens is to auto-center on the curser and move it to the center of the screen. This is unlike any other GIS application, and it's incredibly annoying having the curser jump across the screen when you only zoom one click.

I agree that the map should zoom centered on the curser, but do not move the curser; it just shows down future actions and disorients users that have to re-locate it.

Also when clearing a mission, the screen resets to the home waypoint, even if it's incorrectly set halfway around the world. Clearing a mission shouldn't reset any views.

#### Version

All

No files or tests are named. Start by tracing zoom handling in the flight and planning screens, then inspect the mission-clearing path that resets the view. Done means zooming keeps the cursor in place and clearing a mission preserves the current view instead of returning to the home waypoint.

Written by the indexing model from the issue text.