Faucet DX: fix no-op behavior and add explicit feedback

[snissn]

Fixes the faucet button no-op behavior by improving both backend compatibility and frontend feedback.

What changed

• Faucet server now tries both local RPC methods to set balance:
  • anvil_setBalance
  • hardhat_setBalance
• If neither method is available, returns a clear error instead of silently doing nothing.
• Faucet response now includes the method used and before/after balances.
• UI faucet button now shows explicit outcomes:
  • Faucet funded (X ETH -> Y ETH) when balance was topped up
  • Already funded (Y ETH) when no top-up was needed

Why

• Users reported button clicks that appeared to do nothing.
• Local chains can be Anvil or Hardhat-compatible; only supporting one RPC method is brittle.
• Explicit feedback makes faucet behavior observable and debuggable.

Validation

• pnpm test (29 passing)