feat(badge-nft): add admin badge revocation for fraud prevention

[amankoli09]

Description

Allows the Protocol Admin to revoke a specific Soulbound Badge from a user's UserBadges vector. This is implemented to penalize users who were caught cheating or plagiarizing.

Changes Made

• Added a BadgeRevoked event which is emitted upon successful revocation.
• Implemented the revoke_badge(env: Env, admin: Address, learner: Address, course_id: u32) function in contracts/badge-nft/src/lib.rs.
• Added authentication and admin checks (admin.require_auth()) to verify the caller is the authorized registry.
• Added full test coverage for the revocation flow in contracts/badge-nft/src/test.rs verifying:
  • Successful badge removal.
  • Correct event emission (badge_revoked).
  • Function correctly panics if an unauthorized user attempts to call it.

Acceptance Criteria Met

• The badge is successfully removed from the user's profile.
• Non-admins cannot call this function.

Related Issue

Closes #59

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[Kaylahray]

Hello @amankoli09 Please resolve workflow