Clarify `AOI | Export | Share` language

It is confusing to have multiple terms referring to predictions and exports. We have:
- AOI
- On Explore page/main app, can refer to the selected area before prediction is run
- On Explore page, also refers to selected area after prediction is run
- On Projects list page, refers to exported maps
- Has multiple meanings In frontend/backend codebases, and API
- Export
- On Project individual page, we have "Exported maps" as a grouping with "AOI" referring to individuals
- Has multiple meanings In frontend/backend codebases, and API
- Share
- Explore page's "Export" dropdown states "Create Share URL" and "Copy Share URL"
- Has multiple meanings In frontend/backend codebases, and API

Review the Explore page, Projects list page, and individual project page usages of “AOI,” “Export,” and “Share,” then trace the corresponding frontend, backend, and API terminology. Define consistent meanings for each term and update the affected user-facing and code references; done means the same concepts no longer use overlapping or confusing names.

Written by the indexing model from the issue text.