Convert secrets directory to private git submodule

- Remove secrets files from main repository
- Add secrets as git submodule pointing to private repository
- Secrets repository: ansible/secrets (private)
- Follows security best practice of separating sensitive data

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "secrets"]
+	path = secrets
+	url = ssh://git@git.mymx.me:2222/ansible/secrets.git