Add invoice commands to the CoinPay CLI

[phucnguyen1707]

Summary

• add coinpay invoice create, list, and get to the installed SDK CLI
• support the existing auth flow, invoice filters, wallet routing, readable output, and --json
• normalize invoice API envelopes and safely encode invoice IDs in SDK paths
• document the commands and add subprocess/API-mock coverage

invoice create only creates a draft. It does not send, schedule, mark paid, or move funds.

Tests

• pnpm exec vitest run test/cli-invoice.test.js test/invoices.test.js (32 passed)
• full SDK suite (534 passed, 3 skipped)
• node --check and git diff --check

SDK lint is currently blocked by the existing ESLint 8/9 plugin mismatch in unchanged src/auth.js.