Introduce tournament structure management for Entries Service:

- Add multi-layered entity support for `Turniere`, `Bewerbe`, and `Abteilungen` with tenant isolation.
- Implement Flyway schema migrations with constraints, indices, and default values for `Turniere`.
- Add Kotlin repositories and services for CRUD operations and validation across entities.
- Ensure tenant-safe transactions and implement new exception handling for `LockedException` and `ValidationException`.
- Provide REST APIs with controllers for managing lifecycle, hierarchy, and relationships between entities (`Turniere`, `Bewerbe`, and `Abteilungen`).
- Update Spring configuration with dependency wiring for new services and repositories.

backend/services/entries/entries-service/src/main/resources/db/tenant/V3__turniere_status.sql

@@ -0,0 +1,30 @@
+-- V3: Add status and published_at to turniere, with constraints and index
+-- Context: Roadmap B-1 / A-2 Ergänzung V3
+
+-- Add columns if not exist (compatible with Postgres >= 9.6)
+ALTER TABLE IF EXISTS turniere
+  ADD COLUMN IF NOT EXISTS status VARCHAR(16) NOT NULL DEFAULT 'DRAFT';
+
+ALTER TABLE IF EXISTS turniere
+  ADD COLUMN IF NOT EXISTS published_at TIMESTAMP WITH TIME ZONE NULL;
+
+-- Add CHECK constraint for valid status values (idempotent)
+DO $$
+BEGIN
+  IF NOT EXISTS (
+    SELECT 1 FROM pg_constraint c
+    JOIN pg_class t ON c.conrelid = t.oid
+    WHERE t.relname = 'turniere' AND c.conname = 'chk_turniere_status_valid'
+  ) THEN
+    ALTER TABLE turniere
+      ADD CONSTRAINT chk_turniere_status_valid CHECK (status IN ('DRAFT','PUBLISHED'));
+  END IF;
+END$$;
+
+-- Backfill existing rows to ensure consistent values (no-op if default already applied)
+UPDATE turniere SET status = COALESCE(status, 'DRAFT') WHERE status IS NULL;
+
+-- Index to speed up filtering by status
+CREATE INDEX IF NOT EXISTS idx_turniere_status ON turniere(status);
+
+-- Note: We intentionally keep the DEFAULT 'DRAFT' for safer inserts.