feat: custom branding (#112)

* add first concept

* remove setup status

* split config page in multiple components

* add custom branding docs

* add test email button

* fix invalid email from header

* add migration

* mount images to host

* update docs

* remove unused endpoint

* run formatter

frontend/src/pages/admin/users.tsx

@@ -58,7 +58,7 @@ const Users = () => {
         </Title>
         <Button
           onClick={() =>
-            showCreateUserModal(modals, config.get("SMTP_ENABLED"), getUsers)
+            showCreateUserModal(modals, config.get("smtp.enabled"), getUsers)
           }
           leftIcon={<TbPlus size={20} />}
         >