Stability checkpoint — svc 1.0.53 (wave 4 SB3 surgical fixes)

Captures !194 (wave 4) :
- SB3 RestTestClient stale exclude path (com/example/customerservice → com/mirador/customer)
- SB3 BOM precedence : explicit version pins for spring-boot-test-*
  (forces 3.4.5 over parent 4.0.5 for test-autoconfigure deps)
- pre-java25 overlay copy added to SB3 antrun config (matches compat profile)

Local validation pre-merge :
- ./mvnw -Dsb3 test-compile → reduces 4 compile errors to 1 (CustomerControllerTest constructor mismatch, deferred wave 5)
- ./mvnw -Dcompat test-compile → green
- ./mvnw -Dcompat -Djava17 test-compile → green

Compat re-trigger needed post-tag to validate. SB3 cells expected
to make further progress (PATH_CUSTOMERS + SecurityConfig throws +
RestTestClient exclude + BOM precedence + pre-java25 overlay all in
play). Remaining structural debt : CustomerControllerTest constructor
diff (10 vs 6 params between SB3 overlay and main) — multi-hour
refactor deferred to wave 5.