refactor(person): remove redundant conversations link from header

The co-correspondent chips already link directly to the conversation view
pre-filled with both persons, making the generic "Konversationen anzeigen"
header link redundant. Removed the link and the person_btn_conversations
i18n key from all three locales.

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

frontend/src/routes/persons/[id]/+page.svelte

@@ -199,10 +199,6 @@
                                 {person.firstName} {person.lastName}
                             </h1>
                             <div class="ml-4 flex-shrink-0 flex items-center gap-2">
-                                <a href="/conversations?senderId={person.id}" class="inline-flex items-center gap-1 text-sm font-medium text-brand-navy/60 hover:text-brand-navy transition-colors">
-                                    <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M8 12h.01M12 12h.01M16 12h.01M21 12c0 4.418-4.03 8-9 8a9.863 9.863 0 01-4.255-.949L3 20l1.395-3.72C3.512 15.042 3 13.574 3 12c0-4.418 4.03-8 9-8s9 3.582 9 8z"/></svg>
-                                    {m.person_btn_conversations()}
-                                </a>
                                 {#if data.canWrite}
                                 <button onclick={() => (editMode = true)} class="inline-flex items-center gap-1.5 px-3 py-1.5 text-xs font-bold uppercase tracking-widest border border-gray-300 text-gray-500 rounded hover:border-brand-navy hover:text-brand-navy transition-colors">
                                     <img src="/degruyter-icons/Simple/Small-16px/SVG/Action/Edit-Content-SM.svg" alt="" aria-hidden="true" class="w-3.5 h-3.5" />