Attribution: Übermittler aus users.agency_name statt Agentur-Firma

A3 des Umbaus Agentur-Attribution → User-Profil: Eager Loading der
Detailseite/Vorschau lädt user:id,agency_name; die Legacy-Relation
PressRelease::submittingAgency() (Pseudo-Firma type=agency via
owner_user_id) entfällt. Tests decken Verteiler-Fall, Namensgleichheit
und PM ohne Übermittler ab.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/Http/Controllers/PressReleasePreviewController.php

@@ -33,6 +33,7 @@ class PressReleasePreviewController extends Controller
             ? PressRelease::withoutGlobalScopes()
                 ->with([
                     'company',
+                    'user:id,agency_name',
                     'category.translations',
                     'category.parent.translations',
                     'images' => fn ($query) => $query->orderByDesc('is_preview')->orderBy('sort_order'),