docs(wiki): migrate auth and test references to gitea wiki

- replace local auth and test-plan references with wiki URLs
- delete duplicated local markdown files now covered by wiki
- keep operational docs pointing to the new wiki pages

docs/auto-login-policy-p0-mobile-installed-webapp.md

@@ -74,6 +74,6 @@
 
 ## 8. 관련 문서
 - `docs/AGENTS.md`
-- `docs/auth-flow.md`
+- `https://gitea.hmac.kr/baron/baron-sso/wiki/Authentication-and-Login-Flow.-`
 - `docs/consent_loop_fix_report.md`
-- `docs/test-plan.md`
+- `https://gitea.hmac.kr/baron/baron-sso/wiki/Test-Plan-and-Principles.-`