feat: Renounce admin function

[anonfedora]

Add renounce_admin Function to Crowdfunding Contract

Summary

Implements an irreversible admin renouncement mechanism, allowing the current admin to permanently relinquish control of the crowdfunding contract.

Changes

Closes #79

New functionality (renounce_admin) — the admin can now permanently remove themselves from the contract. Once renounced, all admin-gated actions (e.g. pause/unpause) become inaccessible, as the contract enters a NotInitialized state for admin lookups.

Event emission — a new admin_renounced event is emitted on successful renouncement, enabling off-chain listeners to react to the change in contract governance.

Interface update — renounce_admin is added to the CrowdfundingTrait interface, making it part of the public contract API.

Minor refactor — replaced an explicit .unwrap_or(PoolMetrics::new()) with .unwrap_or_default() for cleaner idiom.

Test Coverage

A dedicated renounce_admin_test.rs module covers:

• Successful renouncement and subsequent loss of admin privileges
• Double-renouncement returning NotInitialized
• Auth enforcement (non-admin callers cannot invoke the function)

Notes

• This action is irreversible — there is no mechanism to reassign admin after renouncement. Callers should be certain before invoking.
• Any integrations relying on admin availability should handle NotInitialized errors gracefully post-renouncement.

[Akshola00]

thanks for your contribution my boss