v4.1.0: DMS email documents, category-specific Nachweis linking, version system

- Save cover email body as DMS document with new 'email' context type
- Show email body separately from attachments in email detail view
- Add per-category DMS document assignment in quarterly confirmation
  (Studiennachweis, Einkommenssituation, Vermögenssituation)
- Add VERSION file and context processor for automatic version display
- Add MCP server, agent system, import/export, and new migrations
- Update compose files and production environment template

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

app/stiftung/agent/urls.py

@@ -0,0 +1,12 @@
+from django.urls import path
+
+from . import views
+
+urlpatterns = [
+    path("", views.agent_index, name="agent_index"),
+    path("chat/", views.agent_chat, name="agent_chat"),
+    path("chat/stream/", views.agent_chat_stream, name="agent_chat_stream"),
+    path("sessions/", views.agent_sessions, name="agent_sessions"),
+    path("sessions/<uuid:session_id>/", views.agent_session_messages, name="agent_session_messages"),
+    path("sessions/<uuid:session_id>/loeschen/", views.agent_session_delete, name="agent_session_delete"),
+]