[FEATURE] Add confirmation modal before deleting a chat session

[adikulkarni006]

Problem
Currently, clicking delete on a session immediately removes it without any confirmation. Users may accidentally delete important conversations.

Expected behavior

• A confirmation modal appears when user clicks delete.
• Modal shows: "Are you sure you want to delete session '[session name]'? This action cannot be undone."
• Buttons: "Cancel" (default) and "Delete" (red/destructive).
• Only after confirmation, the session is deleted.

Technical hints

• Frontend: frontend/src/components/Sidebar.jsx – add state for modal, use existing shadcn Dialog component.
• No backend changes needed (delete endpoint already exists).

Labels: enhancement, good-first-issue, SSoC26

[adikulkarni006]

@annukumar123 Thanks for raising the PR (#370) for this issue. I've reviewed it.

Before merging, please update your branch with the latest main (it's currently out-of-date) so that CI can run properly. Once that's done and the PR passes all checks, maintainer @imDarshanGK can merge it.

Looking forward to the fix!