‼️MERGE PR #1704 FIRST - THESE ARE THE INTEGRATION TESTS ‼️

Checklist

General

• I tested all changes and their related features with all corresponding user types.
• Language: I followed the guidelines for inclusive, diversity-sensitive, and appreciative language.
• I chose a title conforming to the naming conventions for pull requests.

Server

• I strictly followed the server coding and design guidelines.
• I documented the Java code using JavaDoc style.

Motivation and Context

Closes #1737

Description

• Forced spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver in the test context because Spring was picking the H2 driver while using a MySQL JDBC URL, causing driver/URL mismatch and context startup failures.
• Pinned Testcontainers image to mysql:8.0.36 because MySQL 9.3 fails to start with unknown variable 'innodb_log_file_size' in our setup; 8.0.36 is compatible and stable.
• Added retention integration tests covering applicant deletion cascade, professor anonymisation, dry‑run no‑op, unknown user skip, admin skip, mixed batch/idempotency.
• Added job‑level integration tests for cutoff behaviour and dry‑run vs. enabled execution.
• Added scheduling integration test to verify @Scheduled actually fires (using a short cron override).
• Added @AutoConfigureMockMvc to IntegrationTest annotation because integration tests use/expect MockMvc; without it, the bean isn’t created and context loading fails.
• Added @ActiveProfiles("test") to IntegrationTest annotation to ensure the test profile is always active so the test DB/Testcontainers configuration is consistently applied.

Review Progress

Code Review

• Code Review 1

Manual Tests

• Test 1