Full-stack achievement system for SkillTree with backend (NestJS) and frontend (SvelteKit):
- 26 achievements across 7 categories (XP, Skills, Levels, Activities, Streak, Branches, Special)
- 5 rarity tiers (Common → Legendary) with distinct styling
- Auto-unlock after XP gain, skill creation, and activity logging
- Celebration animation on unlock with sparkle effects
- Achievements page with category filters and progress tracking
- IndexedDB offline support with local condition evaluation
- Backend seeds achievements on startup, checks conditions after mutations
- Stats overview extended with achievement counter
- i18n translations (DE + EN)
Also adds docs/MONETIZATION_REPORT.md with ranked analysis of all apps.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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