feat: add ability to duplicate a segment with user-defined name (#5259)

[sbhrwlr]

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Changes

Added a new modal component CreateDuplicateSegmentModal.tsx to create duplicates of segments by copying their data without IDs.

Integrated this modal into SegmentsPage.tsx with a new duplicateSegment function that opens the modal and calls a callback on submission.

Added a "duplicate" button for each segment that triggers duplication using the modal and creates the new segment via API, showing success/error toasts.

Adjusted UI states to disable buttons during creation/removal to handle loading properly.

How did you test this code?

Step 1: Navigate to the Segments page in the application.
Step 2: Find an existing segment from the list.
Step 3: Click the "duplicate" (copy) button next to the chosen segment.
Step 4: In the modal, enter a name for the new segment.
Step 5: Submit the form to create the duplicate segment.
Step 6: Verify the modal closes, the new segment appears in the list, and a success toast shows with the original segment’s name.
Step 7: Try submitting with an empty name to confirm the submit button is disabled, and test canceling the modal closes it without changes.
Step 8: Simulate an API failure (if possible) and verify the error toast appears.
Step 9: Confirm the duplicate and remove buttons are disabled during creation/removal loading states.

Note: Tested for feature specific segments as well.

Added below recording:

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[matthewelwell]

Hi @sbhrwlr, thanks very much for the contribution, however this work is already in progress by the Flagsmith team - see PRs #5393 and #5394.

Please make sure that you reach out to the Flagsmith team before starting any work in the future so we can avoid duplication of effort like this. We'd love to receive PRs on other open issues whenever you have the time.

I'm going to go ahead and close this PR based on this.