Round 19: Competition system, German curriculum learning, enhanced notebooks, student dashboard

- Fix portfolio-view.tsx: replace entry.isPublic with form.isPublic (runtime error)
- Add Competition system: 5 Prisma models (Competition, CompetitionParticipant, CompetitionReward, CompetitionLeaderboard, RewardClaim)
- Add German curriculum learning: 4 Prisma models (SubjectTopic, SubjectLesson, LessonQuestion, StudentAnswer)
- Add 12 API routes for competitions and rewards
- Add 7 API routes for subject topics, lessons, questions, and student answers
- Create competitions-view.tsx with full CRUD, leaderboard, rewards, registration
- Enhance notebooks-view.tsx with 'Lernen' tab for German curriculum subjects
- Add student-specific dashboard with Papier sparen banner, notebook quick access, learning progress
- Add competitions to teacher and student navigation
- Add 130+ i18n keys for DE and EN (competitions, rewards, learning, environment)
- Enhanced student nav with competitions and notebooks
- DSGVO-compliant reward claims with status lifecycle

src/lib/store.ts

@@ -28,7 +28,8 @@ export type ViewName =
   | 'homework'
   | 'portfolio'
   | 'timetable'
-  | 'resources';
+  | 'resources'
+  | 'competitions';
 
 export interface CurrentUser {
   id: string;