Stability checkpoint — svc 1.0.56 (wave 7 SB3 Jackson V3 isolation + ADR-0061)

Captures !197 (wave 7) :
- ADR-0061 : 14-entry SB3/SB4 incompatibility catalog (living doc)
- 3 SB3 overlays : RecentCustomerBuffer + OpenApiConfig (main + 2 tests)
- 2 SB3 BOM pins : spring-boot-starter-hateoas + springdoc 2.7.0

Result : 535 SB3 unit tests run (was 0). 4 errors remain (KafkaConfigTest
V3 transitive leak via Spring Kafka — deferred per ADR-0061 Entry 4).
Default SB4 profile : intact (12/12 tests on RecentCustomerBufferTest +
KafkaConfigTest pass).