Proposal: Spanish UI locale (Terms + reset acknowledgements)

[DSGM-GMSD]

Feature Description

Add a Spanish locale for the GUI, including the first-run Terms of Use and the mandatory pre-reset acknowledgements, with the same legal meaning as the current English.

Motivation

The window already does the important work: Terms acceptance, the 8-point reset warning, the physical-maintenance checkbox, and the second responsibility confirmation. Those texts are what a Spanish-speaking owner needs to understand before any write. They are all hardcoded in English in maintenance_counter_app.py today.

I would like to contribute a Latin American Spanish catalog (es) and keep English as the default.

Proposed Solution

1. Extract user-facing copy into a small catalog (current English wording unchanged as the fallback).
2. Ship es with the same structure: Terms (DISCLAIMER), RESET_WARNING, ACK_PHYSICAL, ACK_RESPONSIBILITY, SAFETY_SHORT, buttons, and dialogs.
3. Pick the language from the existing settings JSON (new lang field) or the Windows locale. English remains the fallback.
4. Do not bump TERMS_VERSION unless you want people who already accepted v2 to re-agree. The Spanish would be a translation of the same v2 terms, not a new agreement.
5. Leave model_db.py, pad names from the database, USB/protocol tokens, and operation-log event names in English.

Docs and the GitHub Pages site (USER_GUIDE.md, TERMS_OF_USE.md, docs/faq.html) can stay English in this first PR.

Alternatives Considered

• Hardcoding Spanish in the .py files — blocks the next language and makes review harder.
• Translating the website/docs in the same PR — larger review, different audience.
• Changing TERMS_VERSION on a same-meaning translation — would force a re-accept for no legal change.

Scope / Effort Estimate

Medium — one GUI file plus a string catalog. tests/test_operations.py should stay green if exception strings in operations.py remain English (or keep English as default).

Questions

• Is es (generic Latin American Spanish) acceptable, or do you prefer es-MX / es-ES?
• Should people who already accepted Terms v2 see Spanish without accepting again?
• Do you want an in-app language control, or OS locale only for the first version?

Happy to send this as a PR once the approach looks right.