fix(tenants): make SMTP password field visible in admin panel

neverReadable blocked the field everywhere including the admin UI.
Changed to allow read for authenticated users only, so the field
shows in admin but stays hidden in unauthenticated API responses.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/collections/Tenants.ts

@@ -220,7 +220,7 @@ export const Tenants: CollectionConfig = {
                     description: 'Leer lassen um bestehendes Passwort zu behalten',
                   },
                   access: {
-                    read: neverReadable, // Passwort nie in API-Response
+                    read: ({ req }) => !!req.user, // Admin kann lesen, API ohne Auth nicht
                   },
                   hooks: {
                     beforeChange: [