Add comment field to user profile in admin panel

- Prisma: User.comment String? column + migration
- UserContactEditor: comment shown in view mode, textarea in edit mode
- updateUserContact action: saves comment to DB

prisma/migrations/20260506100000_add_user_comment/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "User" ADD COLUMN "comment" TEXT;

prisma/schema.prisma

@@ -23,6 +23,7 @@ model User {
   banned        Boolean?  @default(false)
   banReason     String?
   banExpires    DateTime?
+  comment       String?
   createdAt     DateTime  @default(now())
   updatedAt     DateTime  @updatedAt