CONTRACTS: Implement Token Allowance and Delegation

[truthixify]

Description
Add allowance mechanism allowing token owners to delegate transfer rights to other addresses with configurable limits and expiration.

Files to Modify

• contracts/manage_hub/src/allowance.rs - Create allowance module
• contracts/manage_hub/src/types.rs - Add allowance structures
• contracts/manage_hub/src/membership_token.rs - Integrate allowance checks
• contracts/manage_hub/src/lib.rs - Add allowance endpoints

Key Changes Required

• Allowance Storage - Store allowance mappings per token
• Approve Function - Allow owners to grant allowances
• Transfer From - Enable delegated transfers using allowances
• Expiration - Add time-based allowance expiration
• Revocation - Allow owners to revoke allowances
• Query Functions - Add functions to check allowances

Acceptance Criteria

• Implement approve function to set allowances
• Add transfer_from function for delegated transfers
• Store allowance amounts and expiration times
• Emit Approval events when allowances are set
• Implement revoke_allowance function
• Add get_allowance query function
• Support partial allowance consumption
• Prevent allowance abuse with proper validation

[drips-wave]

This issue has been added to the Stellar Wave Program and is worth 200 Points.

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[Iwueseiter]

@Iwueseiter has applied to work on this issue as part of the Stellar Wave Program's 2nd wave.

Hello Maintainer,

My name is Iwueseiter, and I am a smart contract developer with solid experience in Rust. I have previously contributed to Stellar open-source projects and am familiar with the ecosystem and contribution standards.

I am confident in my ability to implement the task as specified, following best practices and project guidelines. I can deliver the solution within an estimated timeline of 2 days.
Thank you for your consideration.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Iwueseiter to this issue.