Develop AR app for urban co-planning

I am looking for an AR app developer, who can develop a working demo for my field testing and if both parties are satisfied, who would continue in developing the app further.

What I am expecting from the app:
placing 3D objects in AR outdoors - objects like tree, bench, trash bin, etc. (we can use free models - no specific look is needed right now)
registering the position of the placed objects with GPS locations (exportable as csv/json, or something similar)

What I will want in the future:
being able to see others' objects - objects somebody placed in my area - comment/vote on them?
change/add/edit objects - only me as the administrator of the app

What I am not sure about:
platform - Can it run as a web app? Should it be a stand-alone app - Android/iOS?

My inspiration for the app - something I am hoping to get at the end:
https://communitar.com/
https://urbanar.app/

I am happy to chat/call with anyone serious about the job. My budget is not really set as I am not sure how much the first demo can cost. Ideally, we would have the first demo ready in a couple of weeks...

Minimum app requirements:
I need the app to place 3-5 testing objects in AR
I need the app to save location (lat/long) and type of the object
I need „export“ function, where list (csv/json) of points (lat/long+type of object) will be available.
I do not have any graphics yet.
I need working demo for first test – please see example at https://communitar.com/about/
I need cost estimate for my project budget before I can move on.

If you have any questions, please let me know...

thanks
Jirka