Add ability to purge historical sessions in batch

[FosanzDev]

WHAT DOES THIS DO?

(Fixes issue: "Add ability to purge historical sessions in batch​ #2603 ")

Adds new section with a "select" button that when clicked, you can select threads to bulk delete them.

Note: Frontend implementation can be changed based on feedback. Maybe instead of a visible button add it on contextual menu in the three-dot menu to start the "selection" process. Not a professional frontend guy tho

Note: Three dot menu for threads are now permanently visible on mobile view too, which couldn't be seen before

POC: This video proofs its functionality both in desktop and mobile frontends

Screencast.from.2026-02-23.18-27-58.webm

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Summary by cubic

Adds bulk deletion of historical sessions from the sidebar with a selection mode, count-based confirmation, and toasts. Implements server/client support and i18n updates to address #2603.

• New Features
  • Backend: DELETE /project/threads accepts DeleteThreadsRequest.threadIds; checks auth and authorship before deleting each.
  • Frontend: Sidebar “Select” toggle with checkboxes; disables navigation while selecting; bulk delete button shows selected count and confirm dialog; clears current/resumed thread if deleted; three-dot menu always visible on mobile.
  • API: Added ChainlitAPI.deleteThreads(threadIds).
  • i18n: Added “select” action and plural delete descriptions across locales.

^{Written for commit 8fc83ed. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 24 files

[dokterbob]

Thanks for the contrib @FosanzDev! It seems there are are a bunch of translations in your PR which are unrelated to the issue. Could you please remove them? (They are welcome in a separate PR.)

[FosanzDev]

@dokterbob maybe I'm not seeing something! Translations are needed for the "Select" button and for the multiple thread selection dialog.
One commit is for the core functionality using only en-US, the other one is for adding the rest of the languages.
Hearing back from you!

[github-actions]

This PR is stale because it has been open for 14 days with no activity.

[github-actions]

This PR was closed because it has been inactive for 7 days since being marked as stale.

[tuncpolat]

Hi @FosanzDev , I noticed this PR was closed. Could you help me understand the reasoning behind it? It seems like a really useful functionality. Thanks!

[FosanzDev]

Hi @tuncpolat I don't really know this was closed. It seems that it was forgotten long enough for the github actions bot to mark it as closed hahaha.
Maybe @dokterbob can you take a look and reopen this?