feat: a custom system's words in the shops and the bank button

[over2take]

The shop window's messages, its receipt and the server's refusals (data/shopRules refusalText), the steps for stocking an empty shop, and the SHOP, VIEW_BANK and SHOP_CATALOGUES buttons ask for their words with the text they show today. A custom system that calls its shops MERCHANTS reads 'NOTHING HERE THIS MERCHANT WOULD BUY' and 'THE MERCHANT PAYS YOU'; one that renamed nothing, and every built-in system, reads exactly as before. The admin's SHOP_CATALOGUES button moved into this piece because the shop's own text names it.

Custom systems have no shops yet (shopsAvailable knows only the built-in systems), so none of this shows until shops are turned on for them. Lines no custom system can reach yet - the cyberware notes, and placement into CWN's slots - keep today's text and are noted for the pieces that make them reachable.

Summary

Test plan

• Tested locally
• Tests pass

Pre-merge checklist

Code quality:

• Code follows project style
• No breaking changes (or clearly documented)
• No console errors or warnings

Version & Release:

• Version bumped? If releasing to users, update:
  • frontend/package.json version
  • docker-compose.yml APP_VERSION
  • CHANGELOG.md with release notes
• GitHub Actions will auto-tag Docker images with the new version

Before merging to main:

• All tests passing
• PR reviewed and approved
• Branch is up to date with main
• No merge conflicts

Related issues