Upsunvalidator

- Renames `templates` as `examples in comments and method names. Previous methods exist as wrappers only, but will be deprecated in a future release.
- Restructures tests to leave only `examples` within the package, not the tests or invalid cases.
- Reinstates CLI as a local testing tool, as this makes updating validation when working with MCP a smoother process instead of rewriting/committing a `test.py` file. This adds but does not change previous behavior. Also adds an `examples` command to list, and an `--example` option flag to validate built-in examples
- Updates missing items in the CHANGELOG

Multiple small changes made ahead of internal demo:

- Adding valid tests for hugo, django-pgvector, and django-redis-celery
- Fixed up sorting hugos between valid and invalid

Release tools: changed from `flit` to `setuptools_scm`.

Automatic versioning for releases was implemented.

All tests were moved within the package itself.

New tag to bundle previous incremental changes.