feat: libvirt setup

fix: ip assigment index
feat: default username

lnvps_db/migrations/20250328220956_fixes.sql

@@ -0,0 +1,4 @@
+-- Add migration script here
+ALTER TABLE vm_ip_assignment DROP KEY ix_vm_ip_assignment_ip;
+alter table vm_os_image
+    add column default_username varchar(50);