ethForward: check ETH/IPFS availability and drop ropsten support

[3alpha]

Summary

Enhances the ethForward middleware to fail fast with clear user-facing messages when required services are unavailable, and removes legacy ropsten handling from the module.

What Changed

• Added preflight availability checks before proxying for:
  • Ethereum JSON-RPC API
  • IPFS API
• Added friendly HTML responses when ETH, IPFS, or both are unavailable.
• Reused existing ethForward error handling paths and improved mapping for proxy/ETH connectivity failures.
• Replaced duplicated ETH RPC hardcoded usage in-module with a shared mainnet constant.
• Removed ropsten support from ethForward:
  • network typing is now mainnet-only
  • removed ropsten/.test resolution paths
  • removed ropsten view helpers and references

User-Facing Behavior

• If ETH or IPFS is unavailable, ethForward now returns a clear page indicating:
  This feature is only available when running both IPFS and Ethereum nodes.

Scope

• Only ethForward-related files were modified.

Validation

• Verified no diagnostics errors in modified ethForward files via editor checks.

[github-actions]

🚀 Deployed on https://69e794b33a226600a91a0c0b--objective-borg-9eeae5.netlify.app

[Pol-Lanski]

oh oh... bad news.

Installed:
dappmanager.dnp.dappnode.eth: 0.2.71, branch: feature/ethforward-api-availability-mainnet-only, commit: 403c715

In a machine that does NOT have full ETH node.

Tests:
vitalik.eth -> works
cowswap.eth -> it forwards me to https://about.ipfs.io/