Major German translation rework (01/12/2024)

[Wuzzy2]

This PR is a major translation work of the German translation. I felt this was neccessary because of many mistakes and just missing translations.

Mistakes in current German translation (that this PR fixes, hopefully) include:

• Outright incorrect/misleading translations
• Missing words
• Text does not fit into widgets
• Typos

After my first failed attempt to update the German translation (#7602), I’ve had another go under master.

I used lupdate and some manual merging of my previous work to get this done.

This was my lupdate line:

lupdate -locations none -I include plugins plugins/* plugins/*/* src/* src/*/* -ts data/locale/de.ts

This is loosely based on what I found in CMake files and I'm not sure if this line captures every string in LMMS, but it seems close. If I missed an important directory, please let me know. The line looks a bit flawed IMO. I would love to know the correct lupdate line. Unfortunately, I'm not very good in reading CMake yet.

(I intentionally removed the -no-obsolete argument because it deletes old translations. It is generally a bad idea to delete obsolete translations by default because obsolete translations can still be useful for translators to pick up similar translators. Especially if modules get moved and renamed around all the time. Qt Linguist is quite powerful in that regard. The only case where I recommend this argument is when a translation is complete or near-complete. It's only text, the few bytes you save aren't worth it IMO.)

Features:

• New translations
• More consistent terminology
• Fixed various incorrect / misleading word translations
• Fixed grammar and typos
• Shortened translations that were too big in some UIs
• Preserved existing translations in the TS file (as "obsolete") to not destroy previous work again

The translation is not complete, but it's about 3000/3200. There are many very difficult strings which seem to require expert knowledge. It would be nice if strings had context and/or translator comments (a core feature of the Qt translation system).

This translation was extensively tested at commit 3562bbe. Feel free to do the same.