[bukkybyte]

Summary

Implements issue #69 — allows ChainScope to connect to any Stellar
network seamlessly, both via CLI flag and live TUI hotkey switching.

Changes

New

• src/config/networks.ts — central network registry with Horizon URLs,
  Soroban RPC endpoints, and passphrases for all three networks
• src/hooks/useNetwork.ts — React hook exposing setNetwork() and
  cycleNetwork() for Dashboard integration
• tests/config/networks.test.ts — 12 tests covering URL uniqueness,
  passphrase uniqueness, and resolveNetwork() case-insensitivity
• tests/hooks/useNetwork.test.ts — 11 tests covering cycle logic,
  selection, and UI label formatting

Modified

• src/index.js — --network <mainnet|testnet|futurenet> flag +
  --watch mode with [n] hotkey to cycle networks live
• tests/mocks/horizonMock.ts — mock helpers now accept a network
  param to target any of the three Horizon base URLs
• tests/integration/horizonMock.test.ts — added testnet/futurenet
  mock tests + network isolation assertion
• package.json — widened engine constraint from >=20 <21 to >=20

Acceptance Criteria

• ✅ Data correctly sourced from selected network
• ✅ UI displays current network prominently (coloured banner on every fetch)
• ✅ --network CLI flag works for all three networks
• ✅ [n] hotkey cycles networks dynamically in --watch mode

Tests

42 passing, 0 failing

Closes #69