SEC-2678 fix catalog-info.yaml validation errors

[NnnOooPppEee]

Summary

Automated cleanup of catalog-info.yaml so the entity passes Backstage catalog validation. The same defects were repeated on every catalog refresh and dominated the service:backstage log volume (the "Policy check failed" family was 69% of all logs).

This change does one or more of:

• Removes never-filled placeholder links (PLACEHOLDER-ADD-*-URL, N/A) that are not valid URLs. Real links are kept.
• Normalizes code-lang: tags to lowercase with dashes (e.g. code-lang:TypeScript to code-lang:typescript). Colons are preserved.
• Drops empty or placeholder tags.

No functional or ownership changes. Part of the Backstage logging cleanup tracked in SEC-2678.

Test plan

Backstage re-validates the entity on its next refresh; the repeating Policy check failed for component:default/<name> warning for this repo should stop.

[NnnOooPppEee]

Could a maintainer or code owner of this repo please review, approve, and merge this PR?

It is a low-risk catalog-info.yaml validation fix (removes never-filled placeholder links and normalizes code-lang tags) so this repo's entity stops failing Backstage catalog validation on every refresh. Part of SEC-2678. Thanks!