feat: All alchemy BTC endpoints

[MatiasOS]

Summary

Add automatic Alchemy RPC endpoints for Bitcoin mainnet and Bitcoin testnet4 when an Alchemy API key is present in settings.

Motivation

Alchemy now supports Bitcoin networks. Users who already use Alchemy for EVM chains should get the same “auto‑add RPCs” behavior for Bitcoin networks without manual configuration.

Proposed Solution

When an Alchemy key is saved, append the Alchemy Bitcoin RPC URL(s) to the RPC list for:

• Bitcoin Mainnet (bip122:000000000019d6689c085ae165831e93)
• Bitcoin Testnet (bip122:00000000da84f2bafbbc53dee25a72ae)

Behavior should mirror existing EVM logic:

• Replace the old Alchemy URL if the key changes.
• Remove Alchemy URLs if the key is cleared.
• Avoid duplicates.

Additional Context

Keep parity with current “Alchemy auto‑add” behavior for EVM chains.

Acceptance Criteria

• Saving an Alchemy key adds Bitcoin mainnet RPC to its network RPC list.
• Saving an Alchemy key adds Bitcoin testnet RPC to its network RPC list.
• Changing or clearing the key updates/removes those RPCs without duplicates.