feat(tournament): implement multi-stage tournament support with intermediate and final stages

- Added backend controller for tournament stages with endpoints to get, upsert, and advance stages.
- Created database migration for new tables: tournament_stage and tournament_stage_advancement.
- Updated models for TournamentStage and TournamentStageAdvancement.
- Enhanced frontend components to manage tournament stages, including configuration for intermediate and final rounds.
- Implemented logic for saving and advancing tournament stages, including handling of pool rules and third place matches.
- Added error handling and loading states in the frontend for better user experience.

backend/routes/tournamentRoutes.js

@@ -39,6 +39,11 @@ import {
   updatePairing,
   deletePairing,
 } from '../controllers/tournamentController.js';
+import {
+  getStages,
+  upsertStages,
+  advanceStage,
+} from '../controllers/tournamentStagesController.js';
 import { authenticate } from '../middleware/authMiddleware.js';
 
 const router = express.Router();
@@ -66,9 +71,6 @@ router.post('/groups/manual', authenticate, manualAssignGroups);
 router.put('/participant/group', authenticate, assignParticipantToGroup); // Muss VOR /:clubId/:tournamentId stehen!
 router.put('/:clubId/:tournamentId', authenticate, updateTournament);
 router.get('/:clubId/:tournamentId', authenticate, getTournament);
-router.get('/:clubId', authenticate, getTournaments);
-router.post('/', authenticate, addTournament);
-
 // Externe Teilnehmer
 router.post('/external-participant', authenticate, addExternalParticipant);
 router.post('/external-participants', authenticate, getExternalParticipants);
@@ -88,4 +90,13 @@ router.post('/pairing/:clubId/:tournamentId/:classId', authenticate, createPairi
 router.put('/pairing/:clubId/:tournamentId/:pairingId', authenticate, updatePairing);
 router.delete('/pairing/:clubId/:tournamentId/:pairingId', authenticate, deletePairing);
 
+// Tournament Stages (mehrere Runden)
+router.get('/stages', authenticate, getStages);
+router.put('/stages', authenticate, upsertStages);
+router.post('/stages/advance', authenticate, advanceStage);
+
+// Muss NACH allen festen Pfaden stehen, sonst matcht z.B. '/stages' als clubId='stages'
+router.get('/:clubId', authenticate, getTournaments);
+router.post('/', authenticate, addTournament);
+
 export default router;