Auto-delete expired events via daily scheduled cleanup job

Adds a Spring @Scheduled job (daily at 03:00) that deletes all events
whose expiry_date is before CURRENT_DATE using a native SQL DELETE.
RSVPs are cascade-deleted via the existing FK constraint.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/test/java/de/fete/adapter/out/persistence/EventPersistenceAdapterIntegrationTest.java

@@ -0,0 +1,81 @@
+package de.fete.adapter.out.persistence;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import de.fete.TestcontainersConfig;
+import de.fete.domain.model.Event;
+import de.fete.domain.model.EventToken;
+import de.fete.domain.model.OrganizerToken;
+import de.fete.domain.port.out.EventRepository;
+import java.time.LocalDate;
+import java.time.OffsetDateTime;
+import java.time.ZoneId;
+import java.time.ZoneOffset;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.annotation.Import;
+import org.springframework.transaction.annotation.Transactional;
+
+@SpringBootTest
+@Import(TestcontainersConfig.class)
+@Transactional
+class EventPersistenceAdapterIntegrationTest {
+
+  @Autowired
+  private EventRepository eventRepository;
+
+  @Test
+  void deleteExpiredRemovesExpiredEvents() {
+    Event expired = buildEvent("Expired Party", LocalDate.now().minusDays(1));
+    eventRepository.save(expired);
+
+    int deleted = eventRepository.deleteExpired();
+
+    assertThat(deleted).isGreaterThanOrEqualTo(1);
+  }
+
+  @Test
+  void deleteExpiredKeepsNonExpiredEvents() {
+    Event future = buildEvent("Future Party", LocalDate.now().plusDays(30));
+    Event saved = eventRepository.save(future);
+
+    eventRepository.deleteExpired();
+
+    assertThat(eventRepository.findByEventToken(saved.getEventToken())).isPresent();
+  }
+
+  @Test
+  void deleteExpiredKeepsEventsExpiringToday() {
+    Event today = buildEvent("Today Party", LocalDate.now());
+    Event saved = eventRepository.save(today);
+
+    eventRepository.deleteExpired();
+
+    assertThat(eventRepository.findByEventToken(saved.getEventToken())).isPresent();
+  }
+
+  @Test
+  void deleteExpiredReturnsZeroWhenNoneExpired() {
+    // Only save a future event
+    buildEvent("Future Only", LocalDate.now().plusDays(60));
+
+    int deleted = eventRepository.deleteExpired();
+
+    assertThat(deleted).isGreaterThanOrEqualTo(0);
+  }
+
+  private Event buildEvent(String title, LocalDate expiryDate) {
+    var event = new Event();
+    event.setEventToken(EventToken.generate());
+    event.setOrganizerToken(OrganizerToken.generate());
+    event.setTitle(title);
+    event.setDescription("Test description");
+    event.setDateTime(OffsetDateTime.of(2026, 6, 15, 20, 0, 0, 0, ZoneOffset.ofHours(2)));
+    event.setTimezone(ZoneId.of("Europe/Berlin"));
+    event.setLocation("Test Location");
+    event.setExpiryDate(expiryDate);
+    event.setCreatedAt(OffsetDateTime.now());
+    return event;
+  }
+}