refactor: Remove librenms, add ansible/salt clients

- Remove all librenms references from initializers and configuration
- Keep tailscale as requested (remove netbird plans)
- Add ansible-core (already present) and salt-minion packages
- Create salt-client initializer for minion configuration
- Update roles to replace librenms-agent with salt-client
- Simplify oam initializer to only handle up2date script
- Update README to reflect new architecture and tools

Prepares infrastructure for migration to Salt configuration management
while maintaining tailscale for VPN connectivity.

💘 Generated with Crush

Assisted-by: GLM-4.6 via Crush <crush@charm.land>

initializers/ssh-hardening/configs/tsys-sshd-config

@@ -0,0 +1,20 @@
+Include /etc/ssh/sshd_config.d/*.conf
+HostKey /etc/ssh/ssh_host_rsa_key
+HostKey /etc/ssh/ssh_host_ed25519_key
+KbdInteractiveAuthentication no
+PrintMotd no
+PasswordAuthentication no
+AllowTcpForwarding no
+X11Forwarding no
+ChallengeResponseAuthentication no
+AcceptEnv LANG LC_*
+Subsystem       sftp    /usr/lib/openssh/sftp-server
+UsePAM yes
+Banner /etc/issue.net
+MaxAuthTries 2
+MaxStartups 10:30:100
+PermitRootLogin prohibit-password
+ClientAliveInterval 300
+ClientAliveCountMax 3
+AllowUsers root localuser subodev
+LoginGraceTime 60