chore: import ordering, final parameters, dependency analysis, and update deps

[deer]

A maintenance pass enforcing build hygiene and code style consistency across all modules.

• New build enforcement: Added maven-dependency-plugin (analyze-only, failOnWarning=true) to enforce explicitly declared dependencies; added requireMavenVersion enforcer rule (3.9.14); pinned Checkstyle to 13.3.0 via explicit plugin dependency.
• New Checkstyle rules: CustomImportOrder (third-party → standard Java → static, alphabetically sorted with blank line separators), FinalParameters, UnusedImportsCheck. Removed stale commented-out Workday-specific checks.
• Dependency bumps: Jackson 2.21.0 → 2.21.2, JUnit 6.0.1 → 6.0.3 (switched from junit-jupiter-engine to junit-jupiter-api), Mockito 5.18.0 → 5.23.0, Guava → 33.4.8-jre, Maven compiler plugin → 3.15.0, wrapper → 3.9.14.
• Preview feature removal: Removed --enable-preview flags and JVM forking from maven-compiler-plugin and maven surefire-plugin across all modules.
• Code conformance: Import blocks reordered and parameters made final throughout all source and test files. Module pom.xml files trimmed of now-redundant transitive dependency declarations.

Test plan:

• ./mvnw clean install passes with no dependency warnings and no Checkstyle violations