feat(interfaces): add pair, factory and callee interfaces

src/interfaces/IFluxCallee.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.36;
+
+interface IFluxCallee {
+    function fluxCall(address sender, uint256 amount0, uint256 amount1, bytes calldata data) external;
+}

src/interfaces/IFluxFactory.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.36;
+
+interface IFluxFactory {
+    event PairCreated(address indexed token0, address indexed token1, address pair, uint256 pairCount);
+
+    function feeTo() external view returns (address);
+    function feeToSetter() external view returns (address);
+    function getPair(address tokenA, address tokenB) external view returns (address pair);
+    function allPairs(uint256 index) external view returns (address pair);
+    function allPairsLength() external view returns (uint256);
+    function createPair(address tokenA, address tokenB) external returns (address pair);
+    function setFeeTo(address to) external;
+    function setFeeToSetter(address setter) external;
+}

src/interfaces/IFluxPair.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.36;
+
+interface IFluxPair {
+    event Mint(address indexed sender, uint256 amount0, uint256 amount1);
+    event Burn(address indexed sender, uint256 amount0, uint256 amount1, address indexed to);
+    event Swap(
+        address indexed sender,
+        uint256 amount0In,
+        uint256 amount1In,
+        uint256 amount0Out,
+        uint256 amount1Out,
+        address indexed to
+    );
+    event Sync(uint112 reserve0, uint112 reserve1);
+
+    function factory() external view returns (address);
+    function token0() external view returns (address);
+    function token1() external view returns (address);
+    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
+    function price0CumulativeLast() external view returns (uint256);
+    function price1CumulativeLast() external view returns (uint256);
+    function minimumLiquidity() external view returns (uint256);
+
+    function initialize(address firstToken, address secondToken) external;
+    function mint(address to) external returns (uint256 liquidity);
+    function burn(address to) external returns (uint256 amount0, uint256 amount1);
+    function swap(uint256 amount0Out, uint256 amount1Out, address to, bytes calldata data) external;
+    function skim(address to) external;
+    function sync() external;
+
+    function totalSupply() external view returns (uint256);
+    function balanceOf(address owner) external view returns (uint256);
+    function transfer(address to, uint256 value) external returns (bool);
+    function transferFrom(address from, address to, uint256 value) external returns (bool);
+    function approve(address spender, uint256 value) external returns (bool);
+}