feat: move vault ssh signing into a plugin (C5)

drizzle/sqlite/0051_conscious_blur.sql

@@ -0,0 +1,5 @@
+-- vault_profiles and vault_tokens move to the vault plugin's adopted tables
+-- at activation, and ssh_data.vault_profile_id is copied into the vault
+-- plugin's host settings by a boot migration after this runs. Dropping any
+-- of them here would lose the data first.
+SELECT 1;