Restore client-only modules for split repository The split client repository needs to carry MCP registration, beat registration, Spring Boot starters, and discovery registration without inheriting the main repository JDK upgrade constraints. This restores the client-side module surface on the JDK 8 release base, rebases dependencies onto Spring Boot 2/JDK 8 compatible lines, and expands CI coverage through JDK 25 after local compatibility verification. Constraint: Client artifacts must remain JDK 8 compatible while validating JDK 17, 21, 23, and 25 Constraint: The split repository does not define the release Maven profile, so CI uses ./mvnw -B clean test Rejected: Move the client back under the main repository | it would keep client compatibility tied to admin/bootstrap JDK upgrade timing Rejected: Keep JDK 23 and 25 as local-only checks | CI would not catch future toolchain regressions Confidence: medium Scope-risk: broad Directive: Do not upgrade client runtime dependencies without rerunning the JDK 8 compatibility build Tested: ./mvnw -DskipTests compile Tested: ./mvnw test Tested: JAVA_HOME=/Library/Java/JavaVirtualMachines/zulu-8.jdk/Contents/Home ./mvnw -B clean test Tested: JAVA_HOME=/Users/aias/Library/Java/JavaVirtualMachines/corretto-17.0.13/Contents/Home ./mvnw -B clean test -Prelease Tested: JAVA_HOME=/Users/aias/Library/Java/JavaVirtualMachines/openjdk-21.0.2/Contents/Home ./mvnw -B clean test -Prelease Tested: JAVA_HOME=/Users/aias/Library/Java/JavaVirtualMachines/openjdk-25.0.2/Contents/Home ./mvnw -B clean test Tested: JAVA_HOME=/tmp/shenyu-jdks/jdk-23.0.2+7/Contents/Home ./mvnw -B clean test Not-tested: End-to-end registration against matching admin/bootstrap runtime