Dashboard: Update faucet amount for arc testnet (#8326)

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## PR-Codex overview

This PR adds a new entry for the `Arc testnet` in the `faucet.ts` file, enhancing the functionality to support an additional test network alongside the existing `Sophon testnet`.

### Detailed summary

- Added a comment for `Arc testnet`.
- Introduced a new entry `5042002: 1` for the `Arc testnet`.

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<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

- **New Features**
  - Introduced faucet support for the Arc testnet, allowing users connected to this network to claim test funds.
  - The claim amount on Arc is set to 1, ensuring consistent and predictable claims on that network.
  - Existing networks and the default claim behavior remain unchanged, preserving current user flows while expanding testnet coverage.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: MananTank

apps/dashboard/src/@/utils/faucet.ts

@@ -5,6 +5,8 @@ const customClaimAmounts: Record<number, number> = {
   631571: 0.1,
   // Sophon testnet
   531050104: 5,
+  // Arc testnet
+  5042002: 1,
 };
 
 const defaultClaimAmount = 0.01;