[Soroban] Metadata Refresh from Backend

[Eniola3321]

Labels

soroban nft enhancement

Summary

Allow backend-authorized metadata refreshes.

Background

Virality scores or analytics may change after minting and require updated metadata.

Tasks
Add refresh_metadata().
Restrict to backend signer/admin.
Add 30-day cooldown.
Emit refresh event.
Swagger / API Integration
Document POST /nfts/:id/refresh-metadata.
Add cooldown error response.
Acceptance Criteria

Metadata can be refreshed by authorized backend.

Cooldown is enforced.

[olawale880]

please can i work on the issue

[grantfox-oss]

🦊 GrantFox — @olawale880 has been assigned to this issue as part of the Third Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #703)
2. Your PR will be reviewed by the ANYTECHS maintainers

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