Point docs at git.fejl40.nu after the move from GitHub

- README / CONTRIBUTING: clone from the Gitea repo.
- SECURITY: Gitea has no private security advisories; report to
  support@fejl40.nu instead.
- RELEASING: release URL on Gitea, plus a note that build.yml still uses
  the GitHub-only action-gh-release step, so no releases are produced on
  Gitea yet (server self-update via git is unaffected).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

SECURITY.md

@@ -12,14 +12,13 @@ We support only the latest release. Please update before reporting a bug.
 
 ## Reporting a Vulnerability
 
-**Please do not file a public GitHub issue for security vulnerabilities.**
+**Please do not file a public issue for security vulnerabilities.**
 
 This tool processes sensitive personal data including Danish CPR numbers (national
 identifiers). Security issues should be reported privately so a fix can be prepared
 before public disclosure.
 
-**Report to:** Open a [GitHub Security Advisory](https://github.com/your-org/gdpr-scanner/security/advisories/new)
-(Settings → Security → Advisories → New draft advisory)
+**Report to:** [support@fejl40.nu](mailto:support@fejl40.nu) — put "Security" in the subject line.
 
 Please include:
 - A description of the vulnerability and its potential impact