refactor: consolidate multi-module Maven project into single module

[rpoet-jh]

Merge all 9 sub-modules (pass-core-object-service, pass-core-doi-service, pass-core-file-service, pass-core-user-service, pass-core-policy-service, pass-core-usertoken, pass-core-test-config, pass-core-main, jacoco-aggregate-report-pass-core) into a single Maven module rooted at the repository root.

• Replace parent POM (packaging=pom) with single-module POM (packaging=jar)
• Consolidate all dependencies and plugins into root pom.xml
• Move all Java sources into src/main/java and src/test/java
• Move all resources into src/main/resources and src/test/resources
• Move Dockerfile, entrypoint.sh, init_postgres.sh to repo root
• Update Dockerfile COPY instruction for new JAR artifact name
• Replace aggregate JaCoCo module with single-module coverage report
• Update sonar.coverage.jacoco.xmlReportPaths for single-module layout
• Add Shibboleth repository to root POM
• Add maven-failsafe-plugin for integration test execution

All 179 unit tests pass. Build produces target/pass-core-2.6.0-SNAPSHOT-exec.jar. File content integrity verified via MD5 checksums (183/183 files match).

AI Disclosure: Kiro IDE 0.11.133 with Claude Sonnet 4.6 was used in Spec Mode to make the changes in this PR. Most of the changes are just git renames. I have reviewed the POM consolidation to ensure it contains the needed elements from the multi-module POMs. I have also tested locally using pass-docker.

Important Notes:

• Used Kiro to create StorageFileTest.java to bump the test coverage for SQ. One thing to verify is this method testEquals_uuidNotConsideredInEquality, should uuid be included in equals?

• In pass-support, we will have to update the POMs to use the pass-core-test-config jar file like this:

<dependency>
  <groupId>org.eclipse.pass</groupId>
  <artifactId>pass-core</artifactId>
  <version>2.6.0-SNAPSHOT</version>
  <classifier>test-config</classifier>
  <scope>test</scope>
</dependency>

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
81.6% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[markpatton]

I did some local testing and it is running well. This is a nice simplification.
I also looked through the github actions and I don't see anything that should cause a problem. I think the existing release actions will just work.