Ability to delete segments

🔍 Problem Statement
As a Pelcro admin, I experience offers and segments being permanent once created, which causes growing clutter from deprecated temporary configurations and makes the admin UI harder to navigate over time.

💡 User Story
As an admin, I want to delete or archive deprecated offers and segments, so that only active configurations are visible and the platform remains clean.

🎯 Definition of Done
- Given an offer or segment with no active subscribers, when an admin deletes it, then it is removed from all lists and cannot be selected for new subscriptions.
- This change impacts the UI (Offers and Segments pages) and API (delete endpoints for offers and segments).
- Limitations: deletion blocked if linked to active subscriptions; soft delete (archive) preferred over hard delete.

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Currently, there is no way to delete offers or segments. This causes a significant amount of additional clutter as some segments are temporarily setup for limited time offers and are deprecated. As we move further down the timeline with this platform, these “dead” segments could become dozens. It would also be nice to be able to edit a segment after publication which would allow multiple new offers to be segmented and automated.