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>

classes/server/initializers

@@ -0,0 +1,17 @@
+# Initializers for all servers (one-time provisioning)
+system-setup
+packages
+oam
+system-config
+ssh-hardening
+ssh-keys
+postfix
+2fa
+wazuh
+security-hardening
+salt-client
+user-configuration
+
+# Roles for all servers
+security
+monitoring