feat: Clubs & Organization Management complete
Backend:
- Created routers/clubs.py with full CRUD
- Clubs: list, get, create, update, delete (admin only)
- Divisions: list, create, update, delete (admin only)
- Training Groups: list, get, create, update, delete (admin/trainer)
- Registered clubs router in main.py
- Permission checks: admin for clubs/divisions, trainer for groups
Frontend:
- Complete ClubsPage with 3 tabs (Vereine, Sparten, Gruppen)
- Role-based UI (admin sees all actions, trainer can manage groups)
- Full CRUD forms with modals
- Mobile-responsive card layouts
- Updated api.js with all club/division/group functions
Migration already exists: 002_organization.sql (clubs, divisions, training_groups)
Next: Skills & Methods display (read-only)