ci: Add PR workflows, pre-commit, release updates, and build fixes

[Saul-STFC]

This PR introduces foundational CI/CD pipelines and code quality tooling for our Java repositories. Once merged, this standard setup can serve as a template to bereplicated across our other Java repos.

Changes:

• Added automated PR checks (pr_build.yaml, pr_prek.yaml) to build and validate code on every pull request.
• Pinned GitHub Action hashes and converted simpler steps to native GitHub commands where actions were unnecessary.
• Configured .pre-commit-config.yaml with rules for yamllint and markdownlint to enforce formatting (mirroring other repos)
• Applied the new linting rules across the existing codebase
• Added a maven wrapper (mvnw) and its associated wrapper files to guarantee a consistent Maven version across all development and CI environments.
• Removed unused dummy tests (AppTest.java) and redundant files.

[Saul-STFC]

@Techassi @NickLarsenNZ

[NickLarsenNZ]

Thanks.

Does this supersede #33?

[Saul-STFC]

Thanks.

Does this supersede #33?

Yes it does :)

[Techassi]

Most of this looks good. I left a few small comments.

One thing I cannot comment on at all is the Maven wrapper stuff. CC'ing @lfrancke here.

[Techassi]

This is good to go from my side. @lfrancke still wanted to look at the Maven wrapper changes.

As such, I'm not approving as of yet.

[Saul-STFC]

This is good to go from my side. @lfrancke still wanted to look at the Maven wrapper changes.

As such, I'm not approving as of yet.

That's fine. For context, it was just running mvn wrapper:wrapper so that builds are reproducible.

[lfrancke]

Sorry, I had a quick look and it looks good to me.

One thing: The README still mentions running plain mvn - that should probably be updated as well then?

[Saul-STFC]

Sorry, I had a quick look and it looks good to me.

One thing: The README still mentions running plain mvn - that should probably be updated as well then?

Done (#f2783755) , also while testing I noticed the readme has the wrong demo users, it had user1, user2 etc instead of user01, user02 in the test-env so I have updated that