Add native cert-manager integration for TLS certificates

[tartkri-bot]

Currently, the Helm chart supports ingress but requires manual configuration for cert-manager TLS certificates.

Proposal

Add native cert-manager integration:

• Add ingress.tls.certManager.enabled flag
• Add ingress.tls.certManager.issuerName / clusterIssuerName options
• Auto-generate Certificate resources when enabled
• Document the integration

This would simplify TLS certificate management for users running cert-manager.