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/views.py

@@ -0,0 +1,232 @@
+"""
+Views für den AI Agent.
+
+Endpunkte:
+  POST /agent/chat/        – Neue Nachricht senden (startet neue oder bestehende Session)
+  GET  /agent/chat/stream/ – SSE-Stream für laufende Anfrage
+  GET  /agent/sessions/    – Liste der Chat-Sitzungen (JSON)
+  DELETE /agent/sessions/<id>/ – Sitzung löschen
+"""
+from __future__ import annotations
+
+import json
+import logging
+
+from django.contrib.auth.decorators import login_required
+from django.core.cache import cache
+from django.http import (
+    HttpResponse,
+    JsonResponse,
+    StreamingHttpResponse,
+)
+from django.shortcuts import get_object_or_404
+from django.utils import timezone
+from django.views.decorators.csrf import csrf_exempt
+from django.views.decorators.http import require_http_methods
+
+from .models import AgentConfig, ChatSession, ChatMessage
+from .orchestrator import run_agent_stream
+
+logger = logging.getLogger(__name__)
+
+RATE_LIMIT_PER_MINUTE = 20
+
+
+def _check_rate_limit(user_id: int) -> bool:
+    """Einfaches Rate-Limiting via Django-Cache (Redis). True = erlaubt."""
+    key = f"agent_rl_{user_id}"
+    count = cache.get(key, 0)
+    if count >= RATE_LIMIT_PER_MINUTE:
+        return False
+    cache.set(key, count + 1, timeout=60)
+    return True
+
+
+def _require_agent_permission(user) -> bool:
+    """Prüft ob der Benutzer den Agent nutzen darf."""
+    return (
+        user.is_superuser
+        or user.has_perm("stiftung.can_use_agent")
+    )
+
+
+@login_required
+@require_http_methods(["GET"])
+def agent_index(request):
+    """Einstiegsseite für den Chat (wird als Modal geöffnet, nicht direkt navigiert)."""
+    config = AgentConfig.get_config()
+    return JsonResponse({
+        "provider": config.provider,
+        "model": config.model_name,
+        "allow_write": config.allow_write,
+    })
+
+
+@login_required
+@require_http_methods(["POST"])
+def agent_chat(request):
+    """
+    Startet oder setzt einen Chat fort.
+
+    Body (JSON):
+      {
+        "message": "Wie viele aktive Destinatäre gibt es?",
+        "session_id": "optional-uuid",
+        "page_context": "optional – aktueller Seiteninhalt als Text"
+      }
+
+    Antwort:
+      {
+        "session_id": "...",
+        "stream_url": "/agent/chat/stream/?session_id=..."
+      }
+    """
+    if not _require_agent_permission(request.user):
+        return JsonResponse({"error": "Keine Berechtigung für den AI-Assistenten."}, status=403)
+
+    if not _check_rate_limit(request.user.id):
+        return JsonResponse(
+            {"error": "Rate-Limit erreicht. Bitte warten Sie eine Minute."},
+            status=429,
+        )
+
+    try:
+        body = json.loads(request.body)
+    except (json.JSONDecodeError, ValueError):
+        return JsonResponse({"error": "Ungültiger JSON-Body."}, status=400)
+
+    message = (body.get("message") or "").strip()
+    if not message:
+        return JsonResponse({"error": "Nachricht darf nicht leer sein."}, status=400)
+
+    page_context = (body.get("page_context") or "")[:2000]
+    session_id = body.get("session_id")
+
+    # Session ermitteln oder neu erstellen
+    session = None
+    if session_id:
+        try:
+            session = ChatSession.objects.get(id=session_id, user=request.user)
+        except ChatSession.DoesNotExist:
+            pass
+
+    if session is None:
+        session = ChatSession.objects.create(user=request.user)
+
+    # Nachricht + Page-Context in Cache für Stream-Endpunkt speichern
+    cache_key = f"agent_pending_{session.id}"
+    cache.set(
+        cache_key,
+        {"message": message, "page_context": page_context},
+        timeout=300,  # 5 Minuten
+    )
+
+    return JsonResponse({
+        "session_id": str(session.id),
+        "stream_url": f"/agent/chat/stream/?session_id={session.id}",
+    })
+
+
+@login_required
+@require_http_methods(["GET"])
+def agent_chat_stream(request):
+    """
+    SSE-Endpunkt: streamt die Antwort des Agenten.
+
+    Query-Params:
+      session_id: UUID der Chat-Sitzung
+    """
+    if not _require_agent_permission(request.user):
+        return HttpResponse("Keine Berechtigung.", status=403)
+
+    session_id = request.GET.get("session_id")
+    if not session_id:
+        return HttpResponse("session_id fehlt.", status=400)
+
+    session = get_object_or_404(ChatSession, id=session_id, user=request.user)
+
+    cache_key = f"agent_pending_{session.id}"
+    pending = cache.get(cache_key)
+    if not pending:
+        return HttpResponse("Keine ausstehende Nachricht gefunden.", status=400)
+
+    cache.delete(cache_key)
+    message = pending["message"]
+    page_context = pending.get("page_context", "")
+
+    def event_stream():
+        try:
+            yield from run_agent_stream(
+                session=session,
+                user_message=message,
+                page_context=page_context,
+                user=request.user,
+            )
+        except Exception as e:
+            logger.error("Agent-Stream-Fehler: %s", e, exc_info=True)
+            import json
+            yield f"data: {json.dumps({'type': 'error', 'message': 'Interner Fehler.'})}\n\n"
+
+    response = StreamingHttpResponse(
+        event_stream(),
+        content_type="text/event-stream",
+    )
+    response["Cache-Control"] = "no-cache"
+    response["X-Accel-Buffering"] = "no"
+    return response
+
+
+@login_required
+@require_http_methods(["GET"])
+def agent_sessions(request):
+    """Gibt die Chat-Sitzungen des Benutzers zurück (letzte 20)."""
+    if not _require_agent_permission(request.user):
+        return JsonResponse({"error": "Keine Berechtigung."}, status=403)
+
+    sessions = ChatSession.objects.filter(user=request.user).order_by("-updated_at")[:20]
+    data = []
+    for s in sessions:
+        data.append({
+            "id": str(s.id),
+            "title": s.title or "Neue Unterhaltung",
+            "created_at": s.created_at.isoformat(),
+            "updated_at": s.updated_at.isoformat(),
+            "message_count": s.messages.count(),
+        })
+    return JsonResponse({"sessions": data})
+
+
+@login_required
+@require_http_methods(["GET"])
+def agent_session_messages(request, session_id):
+    """Gibt alle Nachrichten einer Sitzung zurück."""
+    if not _require_agent_permission(request.user):
+        return JsonResponse({"error": "Keine Berechtigung."}, status=403)
+
+    session = get_object_or_404(ChatSession, id=session_id, user=request.user)
+    messages = session.messages.exclude(role="tool").order_by("created_at")
+    data = []
+    for m in messages:
+        data.append({
+            "id": str(m.id),
+            "role": m.role,
+            "content": m.content,
+            "created_at": m.created_at.isoformat(),
+        })
+    return JsonResponse({
+        "session_id": str(session.id),
+        "title": session.title,
+        "messages": data,
+    })
+
+
+@login_required
+@require_http_methods(["POST"])
+def agent_session_delete(request, session_id):
+    """Löscht eine Chat-Sitzung."""
+    if not _require_agent_permission(request.user):
+        return JsonResponse({"error": "Keine Berechtigung."}, status=403)
+
+    session = get_object_or_404(ChatSession, id=session_id, user=request.user)
+    session.delete()
+    return JsonResponse({"ok": True})