Add a DepClean report to the Maven Site Reports section

Is your feature request related to a problem? Please describe.
DepClean findings are currently primarily consumed through Maven console output and optional generated files. This makes the results difficult to browse, share, and revisit, especially when Maven Site is already used to collect project quality and dependency information.

DepClean does not currently appear in the Maven Site “Project Reports” section.

Describe the solution you'd like
Add a Maven reporting goal, such as depclean:report, that integrates with the Maven Reporting API and generates a DepClean page during mvn site.

The page should:

- Appear in the Maven Site “Project Reports” section.
- Be generated at target/site/depclean.html.
- Summarize used and potentially unused dependencies.
- Separate direct, transitive, inherited, and ignored dependencies.
- Display dependency coordinates, scope, and size.
- Respect existing DepClean configuration such as ignoreTests, ignoreScopes, and ignoreDependencies.
- Remain read-only and not modify the project POM.
- Reuse an existing analysis result when possible to avoid running the analysis twice.

The reporting goal should support standard Maven configuration such as:

se.kth.castor
depclean-maven-plugin
${depclean.version}



report

Describe alternatives you've considered
The current console output can be inspected manually, but it is difficult to navigate in CI logs and is not included in the project documentation.

Another option would be an external tool that converts DepClean’s generated data into HTML and copies it into target/site. However, this would require additional configuration and would not integrate naturally with Maven Site navigation or the standard Maven reporting lifecycle.

Additional context
This would make DepClean consistent with other Maven analysis tools that publish their findings through Maven Site. It would also give teams a stable, browsable dependency-analysis view without enabling automatic POM rewriting or build-failure options.