ci: validate community module registry

[itsDNNS]

Summary

• Adds a registry validation script for community module entries and module folders
• Validates registry fields, local installable directories, manifest ID/version consistency, JSON parsing, Python compilation, and i18n key parity
• Adds a GitHub Actions workflow so pull requests and main pushes run the same validation
• Adds unit coverage for valid fixtures, manifest ID mismatches, and i18n key mismatches

Validation

• python3 -m unittest tests/test_validate_registry.py
• python3 scripts/validate_registry.py
• git diff --check
• /tmp/actionlint-docsight-modules/actionlint .github/workflows/validate.yml