Nachrichten: Design-Label, server-seitige Präferenz, mobiler Leerraum fix

backend/src/db.js

@@ -246,6 +246,11 @@ if (msgCols2.length && !msgCols2.includes('read_by_recipient')) {
   db.exec("ALTER TABLE messages ADD COLUMN read_by_recipient INTEGER NOT NULL DEFAULT 0");
 }
 
+// User-Preferences (JSON-Blob)
+const userCols2 = db.prepare("PRAGMA table_info(users)").all().map(r => r.name);
+if (!userCols2.includes('preferences'))
+  db.exec("ALTER TABLE users ADD COLUMN preferences TEXT DEFAULT NULL");
+
 // ── Login-Sicherheit ──────────────────────────────────────────────────────────
 // Spalten für Account-Lockout in users-Tabelle
 const userCols = db.prepare("PRAGMA table_info(users)").all().map(r => r.name);