[Cloning challenges] Clone for a named administrative area

Right now we ask the user to manually adapt the overpass query for a cloned challenge. For example, the Overpass query for a clone of this challenge would start with

/*
THIS IS THE QUERY OF THE CHALLENGE YOU CLONED PLEASE ADAPT BEFORE USING TO AVOID CREATING DUPLICATE TASKS

rel(161993);map_to_area->.a; // state of utah

Now the user has to go to osm.org or nominatim.osm.org to look up the relation ID for the admin area they want to clone the challenge for, and go back in and insert that ID in the right place in the overpass Query input.

That's a lot to ask of someone who has no experience with Overpass and just wants a copy of an existing challenge for their own city / county / state / ...

Functional description of the feature

1. A link or (better) button "Clone For Area..." would pop up a modal with instructions (exact wording to be confirmed)

"You are about to create a clone of this challenge (). This means that that a copy of this Challenge will be created with all the same settings, but for the area you are interested in. The cloned challenge will have the same name, but with the added text "Clone for AREA". You can change this in the next screen. You can also change other settings, for example the preferred aerial imagery to use."

[NOMINATIM SEARCH BOX]

[Clone Challenge button]

2. MapRoulette creates a copy of the challenge and presents the user with the Challenge create screen. This is the same as the current clone implementation, except for the preset title and the adapted overpass query.
3. User confirms any changes and the challenge is populated.

Additional Requirements

• Search should ideally be typeahead / auto-complete
• Search should not return anything smaller than city and anything larger than country

Caveats

• The area may overlap or lie within the area of the source challenge. We need to check for overlapping or containing geometry and disallow this to avoid creating duplicate tasks.
• There is not a single way to limit an overpass query to an OSM boundary relation.

Start by reviewing the current challenge clone implementation and the Challenge create screen described in the issue. Trace how the Overpass query and title are copied, then assess how a Nominatim area search, area-size limits, and overlap checks would fit the flow. Done means a user can select an administrative area, create a safely adapted clone, and review it before population.