Add German translations (de)

[bprobian]

This PR adds a complete German locale (de) for the project.

Included

• src/django_otp_webauthn/locale/de/LC_MESSAGES/django.po
• src/django_otp_webauthn/locale/de/LC_MESSAGES/djangojs.po
• Automatically generated message catalogs based on the existing source strings

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.0%. Comparing base (51b2050) to head (e4ba5df).
⚠️ Report is 35 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #104   +/-   ##
=======================================
  Coverage   100.0%   100.0%           
=======================================
  Files          13       13           
  Lines         747      745    -2     
  Branches       65       63    -2     
=======================================
- Hits          747      745    -2     

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