i18n(de): Update and optimize German translations

[azurivex]

This PR updates and refines some German (de) locale keys for CachyOS Hello. Some missing translations have been added. Additionally, some keys missing from the English (en) locale have been added.

Changes made:

• Tone adjustment: Formal strings were converted into a modern, informal, peer-to-peer tone to match the tone used throughout the locale.
• Updated / translated strings: Strings such as Reset that were not translated into German were translated into German vocabulary. Other strings in German were updated to sound more accurate and natural.
• Added some missing keys: Some keys that were not found in the German locale have been imported from the English locale and translated.

How to test:

You can launch the app locally forced into the German locale to verify translations:
LANG=de_DE.UTF-8 cargo run (you may also just select the German locale in the languages drop-down menu)

Local translations have been verified using cargo run.

Additional notes

• As stated in a comment I made on my commit, this PR is a partial translation and does not include all the missing keys I found in the English locale.
• I am also seeing an issue with the CI that is causing some PRs to fail due to an error reported in the CI log. Example