Added support for rootstock network

[dacarva]

Motivation

The Safe Transaction Service on Rootstock differs from the canonical Gnosis S-T-S API and Rootstock addresses use the EIP-1191 checksum variant.
Without explicit handling, our frontend either failed to fetch/parse transactions or threw bad address checksum errors when encoding calldata with ethers.js.
This PR makes the app Rootstock-compatible while leaving behavior on every other chain untouched.

What’s changed

app/utils/api.ts

• Added dedicated Rootstock gateway (https://gateway.safe.rootstock.io).

• Introduced a two-step fetch flow:
  …/multisig-transactions/?nonce= – get basic tx list & internal transaction.id.
  …/transactions/{id} – fetch txData + detailedExecutionInfo.

• Normalised the response to our common TransactionParams shape:

• Handles nested objects (e.g. to.value, refundReceiver.value).

• Concatenates confirmations into one signatures blob (first sig keeps 0x, subsequent ones drop the prefix – same as Gnosis backend).

app/components/safeHashesComponent.tsx

• Address normalisation only when chainId === "30":

     if (chainId === "30") {
       address = address.toLowerCase();
       to = to.toLowerCase();
       gasToken = gasToken.toLowerCase();
       refundReceiver = refundReceiver.toLowerCase();
     }

• Likewise, safeAddress is lowered in calculateDomainHash for Rootstock.
• Eliminates INVALID_ARGUMENT: bad address checksum on both API-loaded and manually crafted transactions.

UI

• No visual changes; the “Decode Data” popover and other components work as before.

[github-actions]

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[dacarva]

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