test(fixtures): add test project with SVCs, tests, and reqstool status validation

[jimisola]

Summary

Adds tests/fixtures/test_project/ — a minimal Maven project for end-to-end manual validation:

• pom.xml: reqstool-maven-plugin configured with APT processor, Surefire, and assemble-and-attach-zip-artifact goal
• src/main/java/.../Hello.java: @Requirements("REQ_001") on hello()
• src/test/java/.../HelloTest.java: @SVCs("SVC_001") on testHello()
• docs/reqstool/requirements.yml: REQ_001
• docs/reqstool/software_verification_cases.yml: SVC_001 → REQ_001
• README.md: 3-step validation guide (mvn verify → check zip → reqstool status)

Like the Gradle plugin, Maven bundles everything (requirements, SVCs, annotations, test results) into a self-contained zip, so reqstool status needs only a single extract step.

Test plan

• mvn verify compiles, runs tests, and generates target/reqstool/mypackage-0.1.0-reqstool.zip
• zip contains requirements, SVCs, annotations, test results, and reqstool_config.yml
• reqstool status shows REQ_001 implemented, T1 P1, no missing tests or SVCs