Reverse geocode again after submit pin adjustments

## Context
The submit form lets users move the map pin after EXIF extraction or address autocomplete. The plan notes that reverse geocoding after pin movement was deferred.

## Scope
- Trigger reverse geocoding after the user finishes moving the pin.
- Avoid overwriting fields the user has intentionally edited unless the behavior is explicit.
- Debounce requests and handle failures quietly.

## Acceptance criteria
- Moving the pin can update address, city, country, and postal code from the new coordinate.
- Manual edits are preserved or clearly confirmed before replacement.
- Tests cover successful and failed reverse geocoding after movement.