Repo hygiene: CODEOWNERS, PR/issue templates, Dependabot updates

[sugan0tech]

• Description: Improve contributor experience and maintenance.
• Current state: No CODEOWNERS, PR templates, or Dependabot config.
• Tasks:
  • Add .github/CODEOWNERS and PR/issue templates (bug, feature, chore).
  • Add .github/dependabot.yml for Maven and GitHub Actions updates.
• Acceptance criteria:
  • New PRs show a template; Dependabot opens update PRs.
• References: .github/ directory.