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/oam/librenms/check_mk.socket

@@ -0,0 +1,9 @@
+[Unit]
+Description=Check_MK LibreNMS Agent Socket
+ 
+[Socket]
+ListenStream=6556
+Accept=yes
+ 
+[Install]
+WantedBy=sockets.target