Fix multi-step Uniswap swap decoding and transaction display:
1. uniswap.js: In multi-step swaps (e.g. V3 → V4), the output token and
min received amount now come from the LAST swap step instead of the
first. Previously, an intermediate token's amountOutMin (18 decimals)
was formatted with the final token's decimals (6), producing
astronomically wrong 'Min. received' values (~2 trillion USDC).
2. transactions.js: Contract call token transfers (swaps) are now
consolidated into the original transaction entry instead of creating
separate entries per token transfer. This prevents intermediate hop
tokens (e.g. USDS in a USDT→USDS→USDC route) from appearing as the
transaction's Amount. The received token (swap output) is preferred.
3. transactions.js: The original transaction's from/to addresses are
preserved for contract calls, so the user sees their own address
instead of a router or Permit2 contract address.
closes#127
