[Swift Migration] Turn on strict concurrency

[data-sync-user]

We have around 300 errors when turning strict checking on in the build settings (complete).

1. Please turn on the strict concurrency checking,
2. Indicate which errors you are fixing in https://docs.google.com/spreadsheets/d/1aF1CQfD5NzbfZqg3XpfjJf1UAdVhHWHy2t3HAQIUbjo/edit?gid=0#gid=0
3. Make a manageable number of fixes
4. Turn the setting off again
5. PR your work

Note:

We can turn OFF the “Treat Warnings as Errors” build setting locally to build the project while fixing the warnings (for both Apple Clang and Swift Compiler).

Use Xcode 16.2 (not Xcode 26) to work on this incrementally.

Client > Build Settings > Swift Compiler - Upcoming Features

!Screenshot 2025-06-18 at 2.04.07 PM.png|width=476,height=119,alt="Screenshot 2025-06-18 at 2.04.07 PM.png"!

Synchronize who is working on which file: https://docs.google.com/spreadsheets/d/1aF1CQfD5NzbfZqg3XpfjJf1UAdVhHWHy2t3HAQIUbjo/edit?gid=0#gid=0

Add your name and the files you’re modifying.

┆Issue is synchronized with this Jira Task