fix: obscure critical config variables

backend/prisma/schema.prisma

@@ -84,6 +84,7 @@ model Config {
   type        String
   value       String
   description String
+  obscured    Boolean @default(false)
   secret      Boolean @default(true)
   locked      Boolean @default(false)
 }

backend/prisma/seed/config.seed.ts

@@ -1,7 +1,7 @@
-import { PrismaClient } from "@prisma/client";
+import { Prisma, PrismaClient } from "@prisma/client";
 import * as crypto from "crypto";
 
-const configVariables = [
+const configVariables: Prisma.ConfigCreateInput[] = [
   {
     key: "SETUP_FINISHED",
     description: "Whether the setup has been finished",
@@ -83,6 +83,7 @@ const configVariables = [
     description: "Password of the SMTP server",
     type: "string",
     value: "",
+    obscured: true,
   },
 ];