feat(emails): co-founder language, welcome rewrite, and Spanish translations (#208)
## Summary
- **Welcome email rewritten** with benefit-focused content (understand
your finances, smart spending & investing, connect your banks,
private/own your data — no AI/data-mining narrative)
- **All email signatures updated** to reflect both co-founders: Víctor &
Álvaro, Founders of Whisper Money (drip, transactional, and waitlist
templates)
- **`user-lead-invitation.blade.php`** fully wrapped with `{{ __() }}` —
was entirely hardcoded English
- **Promo code email disabled** — removed `SendPromoCodeEmailJob`
dispatch from `ScheduleDripEmailsListener`; test updated to assert it is
not dispatched
- **60 missing Spanish translation keys** added to `lang/es.json`,
alphabetically sorted
## Files changed
- `app/Listeners/ScheduleDripEmailsListener.php`
- `lang/es.json`
- `resources/views/mail/**` (11 blade templates)
- `tests/Feature/Listeners/ScheduleDripEmailsListenerTest.php`
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