CONTRACTS: Add Token Staking Mechanism

[truthixify]

Description
Implement staking functionality allowing token holders to lock tokens for rewards, governance participation, or other benefits.

Files to Modify

• contracts/manage_hub/src/staking.rs - Create staking module
• contracts/manage_hub/src/types.rs - Add staking structures
• contracts/manage_hub/src/rewards.rs - Add reward calculation
• contracts/manage_hub/src/lib.rs - Add staking endpoints

Key Changes Required

• Stake Function - Lock tokens for specified duration
• Unstake Function - Unlock tokens after lock period
• Reward Calculation - Calculate rewards based on stake duration
• Lock Periods - Support different lock period options
• Emergency Unstake - Add emergency unstake with penalties
• Staking Tiers - Implement different staking tiers with benefits

Acceptance Criteria

• Implement stake_tokens function with lock duration
• Add unstake_tokens function with lock period validation
• Calculate and distribute staking rewards
• Emit Staked and Unstaked events
• Add get_stake_info query function
• Support multiple staking tiers
• Implement reward multipliers for longer stakes
• Add emergency unstake with penalty mechanism

[drips-wave]

This issue has been added to the Stellar Wave Program and is worth 150 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.