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>

specs/013-auto-delete-expired/plan.md

@@ -0,0 +1,90 @@
+# Implementation Plan: Auto-Delete Expired Events
+
+**Branch**: `013-auto-delete-expired` | **Date**: 2026-03-09 | **Spec**: [spec.md](spec.md)
+**Input**: Feature specification from `/specs/013-auto-delete-expired/spec.md`
+
+## Summary
+
+Add a scheduled background job that runs daily and deletes all events whose `expiryDate` has passed. Deletion is performed via a native SQL query (`DELETE FROM events WHERE expiry_date < CURRENT_DATE`). Cascade deletion of RSVPs is handled by the existing `ON DELETE CASCADE` FK constraint. No API or frontend changes required.
+
+## Technical Context
+
+**Language/Version**: Java 25, Spring Boot 3.5.x
+**Primary Dependencies**: Spring Scheduling (`@Scheduled`), Spring Data JPA (for native query)
+**Storage**: PostgreSQL (existing, Liquibase migrations)
+**Testing**: JUnit 5, Spring Boot Test, Testcontainers (existing)
+**Target Platform**: Linux server (Docker)
+**Project Type**: Web service (backend only for this feature)
+**Performance Goals**: N/A — daily batch job on small dataset
+**Constraints**: Single native DELETE query, no entity loading
+**Scale/Scope**: Self-hosted, small-scale — typically < 100 events total
+
+## Constitution Check
+
+*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*
+
+| Principle | Status | Notes |
+|-----------|--------|-------|
+| I. Privacy by Design | PASS | Deleting expired data supports privacy goals. No PII logged. |
+| II. Test-Driven Methodology | PASS | Tests written before implementation (TDD). |
+| III. API-First Development | N/A | No API changes — this is a backend-internal job. |
+| IV. Simplicity & Quality | PASS | Single query, no over-engineering. |
+| V. Dependency Discipline | PASS | Uses only existing Spring dependencies (`@Scheduled`). |
+| VI. Accessibility | N/A | No frontend changes. |
+
+## Project Structure
+
+### Documentation (this feature)
+
+```text
+specs/013-auto-delete-expired/
+├── plan.md              # This file
+├── spec.md              # Feature specification
+├── research.md          # Phase 0 output (minimal — no unknowns)
+├── data-model.md        # Phase 1 output
+└── checklists/
+    └── requirements.md  # Spec quality checklist
+```
+
+### Source Code (repository root)
+
+```text
+backend/src/main/java/de/fete/
+├── application/service/
+│   └── ExpiredEventCleanupJob.java          # NEW: Scheduled job
+├── domain/port/out/
+│   └── EventRepository.java                 # MODIFIED: Add deleteExpired method
+└── adapter/out/persistence/
+    ├── EventJpaRepository.java              # MODIFIED: Add native DELETE query
+    └── EventPersistenceAdapter.java         # MODIFIED: Implement deleteExpired
+
+backend/src/test/java/de/fete/
+├── application/service/
+│   └── ExpiredEventCleanupJobTest.java      # NEW: Unit test for job
+└── adapter/out/persistence/
+    └── EventPersistenceAdapterIntegrationTest.java  # NEW or MODIFIED: Integration test for native query
+```
+
+**Structure Decision**: Backend-only change. Follows existing hexagonal architecture: port defines the contract, adapter implements with native query, service layer schedules the job.
+
+## Design
+
+### Hexagonal Flow
+
+```
+@Scheduled trigger
+    → ExpiredEventCleanupJob (application/service)
+        → EventRepository.deleteExpired() (domain/port/out)
+            → EventPersistenceAdapter.deleteExpired() (adapter/out/persistence)
+                → EventJpaRepository native query (adapter/out/persistence)
+                    → DELETE FROM events WHERE expiry_date < CURRENT_DATE
+```
+
+### Key Decisions
+
+1. **Port method**: `int deleteExpired()` on `EventRepository` — returns count of deleted events for logging.
+2. **Native query**: `@Modifying @Query(value = "DELETE FROM events WHERE expiry_date < CURRENT_DATE", nativeQuery = true)` on `EventJpaRepository`.
+3. **Schedule**: `@Scheduled(cron = "0 0 3 * * *")` — runs daily at 03:00 server time. Low-traffic window.
+4. **Logging**: INFO-level log after each run: `"Deleted {count} expired event(s)"`. No log if count is 0 (or DEBUG-level).
+5. **Transaction**: The native DELETE runs in a single transaction — atomic, no partial state.
+6. **Enable scheduling**: Add `@EnableScheduling` to `FeteApplication` (or a config class).