feat: Add PancakeSwap V4 support and test cases

[jetbldr]

Summary

Add support for detecting sandwich attacks on PancakeSwap V4 pools.

Changes

• New protocol parser: Added protocols/pancakev4/pancakev4.go to parse PancakeSwap V4 Swap events
• Updated swap detection: Added PancakeSwap V4 event signature (0x04206ad2b7c0f463bff3dd4f33c5735b0f2957a351e4f79763a4fa9e775dd237) to protocols/swap.go
• Test coverage: Added testCase7PancakeV4 test case using real on-chain sandwich attack data
• Documentation: Updated README.md to reflect PancakeSwap V4 as a separately supported protocol

Background

PancakeSwap V4 uses a different Swap event signature than Uniswap V4:

• Uniswap V4: 0x40e9cecb9f5f1f1c5b9c97dec2917b7ee92e57ba5563708daca94dd84ad7112f
• PancakeSwap V4: 0x04206ad2b7c0f463bff3dd4f33c5735b0f2957a351e4f79763a4fa9e775dd237

Event structure:

Swap(bytes32 indexed id, address indexed sender, int128 amount0, int128 amount1, uint160 sqrtPriceX96, uint128 liquidity, int24 tick, uint24 fee, uint16 protocolFee)

Testing

go test -v -run TestDetectSandwichForBundle/testCase7PancakeV4

All tests pass ✅