Analytics data lifecycle on card deletion

[ShantKhatri]

Summary

Decide and implement what happens to analytics data when a card is deleted.

Contexts

Spec flags this as an open edge case. Needs a decision: hard delete, anonymized retention, or soft delete with expiry.

Tasks

• Document the chosen retention policy
• Implement cascade/cleanup logic on card deletion
• Add a scheduled job if soft-delete with expiry is chosen

Acceptance Criteria

• Deleting a card behaves per the documented policy
• No orphaned analytics rows left behind
• Tests added
• docs updated

Area

backend

Difficulty

Intermediate

[github-actions]

Hi @ShantKhatri,

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