feat(contracts): add remove liquidity example

[SharkHand3]

Motivation

Closes #52.

The repository did not have an Alloy example for removing liquidity from a Uniswap V2-compatible pair. The ethers-rs reference linked in the issue also hardcoded a deprecated RPC endpoint and a private key.

Solution

• add IUniswapV2Pair and IUniswapV2Router02 bindings generated by sol!
• load the RPC endpoint, signer, contract addresses, liquidity, and minimum output amounts from required environment variables
• verify the signer has enough LP tokens and display the pair tokens and reserves
• approve only the requested LP-token amount
• use caller-provided minimum outputs and a bounded 20-minute deadline
• simulate removeLiquidity before sending the removal transaction
• document the example in the README and generated example index

Testing

• cargo check --locked -p examples-contracts --example remove_liquidity
• cargo check --workspace --examples --all-features --locked
• cargo +nightly fmt --all --check
• cargo clippy --workspace --examples --all-features --locked -- -D warnings
• end-to-end execution against a local Ethereum mainnet fork using the deployed Uniswap V2 USDC/WETH pair and router; both the approval and removal receipts succeeded without broadcasting to mainnet