Fix broken links and standardize exercise naming

[mayasrl]

Fixes #588 Fixes #587

This solution refers to which of the apps?

Multiple apps - fixing documentation links and docker-compose naming across the repository.

What did you do to mitigate the vulnerability?

This isn't a vulnerability fix, just maintenance work on documentation and naming consistency:

• Fixed 5 broken links in README files (main README and a few exercise READMEs)
• Standardized naming in 12 docker-compose.yml files to match their OWASP categories
• Renamed a Dockerfile and updated some environment variables to keep everything consistent

The issue was that some exercises had container names from wrong categories (like a5 in an a1 folder), which could confuse people navigating the repo.

Did you test your changes? What commands did you run?

Yeah, I checked all the links to make sure they work now and verified that the docker-compose files have the right naming pattern. No code logic changed, just organizational stuff.

Total: 18 files modified (4 READMEs + 14 config files)