SC: Develop Stablecoin Staking Smart Contract

[Pvsaint]

Description: Create a Soroban smart contract for YieldForge to allow users to stake stablecoins (e.g., USDC) in a single-asset pool and track their balances.

Tasks:

Write a Rust-based contract for staking (deposit/withdraw stablecoins).
Define parameters: user address, amount, asset (e.g., USDC).
Test deposit/withdrawal on testnet with a sample stablecoin.

Acceptance Criteria:

Contract allows users to deposit and withdraw stablecoins on testnet.
User balances are correctly tracked and retrievable.
Contract handles Stellar trustlines for the stablecoin.