Reorder account list when desired

[gnprice]

We should offer a feature for users to rearrange the order of their list of accounts.

This would appear on the choose-account page (or after #1038, might be an option in the choose-account modal and takes you to a separate "manage accounts" page). The general shape of the UI should be:

• First the user indicates they want to manage the list of accounts.
• Then the items in the account list become draggable, for the user to move them around as they please.
• In that mode, there's some way to say "ok, done" and return to the normal version of the UI, where tapping on an item navigates to that account and they're not draggable.

Implementation

The key ingredient for implementing this UI is ReorderableListView, from Flutter's Material implementation.

(In principle it'd be good to have a design for this, which might change some of the details I described above. But this is a feature that people use once, briefly; it makes their Zulip experience better in an ongoing way because now their accounts are in an order that makes sense for them; but then they may not touch the feature itself again for a long time. So I think it's not a high priority to spend design effort on, and we should just implement something with the off-the-shelf ReorderableListView.)

[gnprice]

(In the legacy app, we instead constantly reorder the list automatically: each time you use an account, it moves to the top of the list. Today we heard from beta users who are glad the new app doesn't do that.)

[Pudv95]

ScreenRecording_12-19-2024.16-15-28_1.MP4

Its simple implementation of the ReorderableListView we have to hold the chat we want to reorder and enter the reordering mode then place it accordingly.