Testcontainers 2.0 migration — BOM artifact reorganization

[amavashev]

Tracks the Testcontainers 1.x → 2.x migration. Currently blocks #151.

Why this isn't a Dependabot merge

Testcontainers 2.0 reorganized its BOM. `org.testcontainers:junit-jupiter` is no longer managed by the BOM, so any pom that imports it without an explicit version (relying on ``) fails to build:

```
'dependencies.dependency.version' for org.testcontainers:junit-jupiter:jar is missing.
@ io.runcycles:cycles-admin-service-data ... cycles-admin-service-data/pom.xml line 57
```

Scope of the migration

• Identify the 2.x replacement artifact / new artifact ID (or pin `junit-jupiter` version explicitly if the BOM no longer manages it)
• Update every `@Testcontainers` / `@Container` usage — 2.0 changed defaults around container reuse and lifecycle
• Re-verify all integration tests (full `mvn -B verify` green)
• Sweep AUDIT.md / CHANGELOG.md per release-prep convention

Cross-repo

If the same migration is needed in `cycles-server-events` or `cycles-server`, file companion issues there. The three repos use Testcontainers independently, so each can migrate separately.

Reference

• PR chore(deps): bump org.testcontainers:testcontainers-bom from 1.20.4 to 2.0.5 in /cycles-admin-service #151 (closed): chore(deps): bump org.testcontainers:testcontainers-bom from 1.20.4 to 2.0.5 in /cycles-admin-service #151
• Testcontainers 2.0 release notes (TODO: link)