Overhaul and Complete German Translation

[m2u-84]

Notable Changes

• Add missing new keys and provide German translations
• Make texts more readable and human-friendly by using typographic quotes and proper chars for en dash and horizontal ellipsis
• Fix and improve various compound hyphenations
• Reduce deviations from original English texts in terms of content as well as formatting
• Remove indentations from multi-line strings because they were appearing in the actual UI visualization
• Fix various typos in existing translations and take care of missing and / or superfluous punctuation marks
• Make existing translations more consistent
• Improve and disambiguate German equivalents for keywords ‘prune’ (leans more towards ‘clean’ instead of ‘delete’ now) and ‘theirs’ (previous translation bore the risk of a mixup with the German formal address style ‘Ihre’)
• Mark German translation as complete and remove list of missing keys

Disclaimer: No AI was used to create the code and this PR.