feat(amm): Introduce swap external function with full Natspec documentation

[Neros0]

Description

This PR adds a fully documented swap external function to the TestAMMContract, implementing the classic constant product AMM formula (x * y = k). This enables token swapping within a selected market pool while providing slippage protection, reserve updates, and event hooks for off-chain monitoring.

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✅ Key Features

• New Swap Functionality

function swap(
    bytes32 _marketId,
    uint256 _amountIn,
    uint256 _amountOutMinimum,
    bool _zeroForOne
) external