Standardize Java API package and Maven naming

[prestoncabe]

Summary

Builder API still used the org.acme namespace, while Library API used org.codeforphilly.bdt. Standardize both APIs under the shared project identity with service-specific Java packages:

• Use org.codeforphilly.bdt.builder and org.codeforphilly.bdt.library, moving source and test files to matching directories and lowercasing Builder DTO package names.
• Use Maven group ID org.codeforphilly.bdt for both APIs and rename Builder's artifact to bdt-builder-api.
• Update Library's OpenAPI filter and the Java class reference in BDT.dmn, plus affected documentation and the repository naming convention.

API routes, JSON fields, and decision logic remain unchanged.

Closes #524.

Verification

• Builder API: mvn test — 158 tests passed.
• Library API: mvn test — 15 tests passed.
• Both APIs: mvn package -DskipTests — passed after running the test suites.
• Library Bruno collection against this branch's packaged service on isolated localhost port 18083 — 47 requests and 71 assertions passed.
• Direct requests through decision-service-invoker verified both passing and failing decisions via the renamed Java class; expected OpenAPI routes were present.
• After the final import cleanup: mvn test -Dtest=LibraryBenefitResourceTest — 3 tests passed.
• git diff --check — passed.

Documentation impact

• Updated the root naming convention, Library source/test paths, and Builder's documented native executable filename.