Update German translations (#2917)

* Update German translations

* Apply suggestions from code review

Co-authored-by: Felix Siebeneicker <[email protected]>

* Further suggestions from code review

* Apply further suggested change

* Apply suggestions from code review

* Apply suggested changes from PythooonUser

* Update src/locale/locales/de/messages.po

* Apply suggestions from code review

Co-authored-by: cdfzo <[email protected]>

* Apply suggestions from @cdfzo's code review manually

* Apply suggestion from @cdfzo's code review manually

* Update messages.po

* Update src/locale/locales/de/messages.po

Co-authored-by: Felix Siebeneicker <[email protected]>

* Update messages.po

* Apply suggestions from code review

Co-authored-by: Felix Siebeneicker <[email protected]>

* Update src/locale/locales/de/messages.po

* Update messages.po

* Change `Benachrichtigungen` to `Mitteilungen` in line with #2805

* Apply suggestions from code review

Co-authored-by: Felix Siebeneicker <[email protected]>

* Apply suggestions from code review

Co-authored-by: Felix Siebeneicker <[email protected]>

* Change four usages of Benutzerhandle

* Update messages.po

* Update src/locale/locales/de/messages.po

* Add credits

* Update messages.po

* Add new translated strings following merge

* Update messages.po

* Update messages.po

* Update german translations by @cdfzo

* Update german translations

* Apply suggestions from code review

Co-authored-by: surfdude29 <[email protected]>

* Correct translations from pr review

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Co-authored-by: surfdude29 <[email protected]>

* Update revision date of messages.po

* Update messages.po

* Update messages.po

* Delete superseded strings

* Add new translations

* Update messages.po

* Apply suggestions from code review

Co-authored-by: cdfzo <[email protected]>

* Apply suggested change from code review by @cdfzo

* Update revision date of messages.po

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Co-authored-by: Felix Siebeneicker <[email protected]>
Co-authored-by: cdfzo <[email protected]>