V6.1 Group Assign Patch

Added:
- Manual Group Assign board in Tournament tab
- Assign teams to Group A/B/C/D/E before fixture generation
- Team seed/order controls: Up / Down
- Save Group Assign API
- Generate Tournament now uses saved manual groups first
- If no manual groups are saved, old auto-distribute behavior still works

Workflow:
1. Create/select tournament
2. Select group count
3. In Group Assign, move teams into groups
4. Use Up/Down to set order
5. Save Group Assign
6. Generate Tournament Fixtures

Fixture order per group:
Seed 1 vs Seed 2
Seed 3 vs Seed 4
Seed 5 vs Seed 6
Odd final seed gets Bye qualifier