Add German translations for Tier 2 (Engagement) pages
- features-DE.md: Complete German translation of Features page (345 lines) covering all QET capabilities, professional documentation, export options, real-world use cases, and industry support
- community-DE.md: Full German translation of Community page (339 lines) with contribution pathways, community resources, governance, and recognition for contributors
- tips_and_tricks-DE.md: Comprehensive German translation of Tips & Tricks page (510 lines) with advanced workflows, performance optimization, collaboration strategies, and industry-specific patterns
- languages.md: Updated translation status showing all Tier 2 pages now complete in all three languages (English ✅, Français ✅, Deutsch ✅)
Tier 1 + Tier 2 now fully translated to German and French (8 complete pages per language).
Multi-language wiki expansion complete for onboarding and engagement tiers.
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