feat(smart-contract): Implement Agent Staking and Bond Mechanism

[devJaja]

Summary

Add a staking requirement for agent registration where agents must lock XLM as a bond. The bond is slashed on misbehavior (downtime, poor quality) and returned on deregistration.

Motivation

Currently, any entity can register as an agent with zero cost, enabling spam registrations. A staking bond creates economic accountability and filters low-quality agents.

Acceptance Criteria

• register_agent requires minimum XLM bond (configurable via admin-set minimum)
• Bond stored in contract data keyed by agent ID
• deregister_agent returns bond to agent owner after cooldown period (24h)
• slash_bond admin function reduces bond by penalty amount for violations
• Bond amount included in AgentRecord struct
• Events emitted: BondLocked, BondSlashed, BondReturned
• Gas estimation updated for staking operations
• Unit tests covering: register with insufficient bond, slash, return, double-slash prevention

Files to Modify

File	Action
smart-contracts/contracts/agent_registry/src/lib.rs	Add bond storage, slash, and return logic
smart-contracts/contracts/agent_registry/src/events.rs	Add BondLocked, BondSlashed, BondReturned events
smart-contracts/contracts/agent_registry/src/types.rs	Extend AgentRecord with bond_amount field
smart-contracts/contracts/agent_registry/src/errors.rs	Add InsufficientBond error code
smart-contracts/contracts/agent_registry/src/test.rs	Add bond-related unit tests

How to Contribute

1. Create branch feat/agent-staking-bond
2. Define bond storage in contract data ( persistent storage )
3. Modify register_agent to accept and validate bond payment
4. Implement cooldown timer for bond return
5. Add slash logic with admin authorization check
6. Write comprehensive unit tests
7. Run cargo test and cargo clippy before submitting PR

[retkatmun]

Hi Maintainer,

I’m a smart contract and full-stack developer and would love to contribute to this issue. I’m an experienced contributor with hands-on expertise in Rust, Soroban, Cairo, and TypeScript.

I’m passionate about building secure, scalable blockchain solutions, with a strong emphasis on writing clean and maintainable code. Based on the scope of this issue, I’m confident I can deliver a complete solution within 24 hours of assignment.

I’d greatly appreciate the opportunity to contribute and help move this forward.

[grantfox-oss]

🦊 GrantFox — @retkatmun 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 #242)
2. Your PR will be reviewed by the Epta-Node maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Third Campaign campaign!

@retkatmun's PR #282 was approved and merged by @devJaja.

🏆 @retkatmun: You earned 40 FoxPoints for this contribution! Your current tier: Builder (1,108 total points). Track your full progress on GrantFox.

👏 Great work, @retkatmun! Keep contributing to Epta-Node.