fix: add captcha.error translation and protected DbContext constructor

[juljanblischke]

• Add missing auth:captcha.error translation key in EN and DE auth.json

• Add protected constructor to AppDbContext for DbContext inheritance support (required by Pro's ProDbContext which extends AppDbContext)

  Description

  Fix missing auth:captcha.error translation and add protected DbContext constructor to support inheritance in Pro repository.

  Related Issue

  N/A (Internal bug fixes for Pro integration)

  Type of Change

  • 🐛 Bug fix (non-breaking change that fixes an issue)

  Changes Made

  • Add missing auth:captcha.error translation key in English (frontend/src/i18n/locales/en/auth.json)
  • Add missing auth:captcha.error translation key in German (frontend/src/i18n/locales/de/auth.json)
  • Add protected constructor to AppDbContext for DbContext inheritance support (backend/src/ExoAuth.Infrastructure/Persistence/AppDbContext.cs)

  Screenshots

  N/A

  Testing

  • Unit tests pass locally
  • Integration tests pass locally
  • Manual testing completed

  Test Instructions

  1. Start the application with CAPTCHA enabled
  2. Trigger a CAPTCHA error scenario
  3. Verify the error message displays correctly in both EN and DE
  4. For DbContext change: Verify Pro API can start and use ProDbContext which extends AppDbContext

  Checklist

  • My code follows the project's code style guidelines
  • I have performed a self-review of my code
  • I have commented my code, particularly in hard-to-understand areas
  • My changes generate no new warnings
  • New and existing unit tests pass locally with my changes

  Additional Notes

  The protected DbContext constructor follows the standard EF Core pattern for DbContext inheritance. This allows derived classes (like ProDbContext) to pass their own typed DbContextOptions while the base class accepts generic DbContextOptions.