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/views/land.py

@@ -14,8 +14,8 @@ import qrcode.image.svg
 from django.contrib import messages
 from django.contrib.auth.decorators import login_required
 from django.core.paginator import Paginator
-from django.db.models import (Avg, Count, DecimalField, F, IntegerField, Q,
-                              Sum, Value)
+from django.db.models import (Avg, BigIntegerField, Count, DecimalField, F,
+                              IntegerField, Q, Sum, Value)
 from django.db.models.functions import Cast, Coalesce, NullIf, Replace
 from django.http import HttpResponse, JsonResponse
 from django.shortcuts import get_object_or_404, redirect, render
@@ -274,24 +274,25 @@ def land_list(request):
         lands = lands.filter(aktiv=False)
 
     # Annotate with verpachtungsgrad and numeric casts for natural sorting
-    # Prepare numeric versions of textual fields by stripping common non-digits
+    # Use regexp_replace to strip ALL non-digit characters for safe integer casting
+    from django.db.models import Func
+
+    class RegexpReplace(Func):
+        function = "REGEXP_REPLACE"
+        template = "%(function)s(%(expressions)s, '[^0-9]', '', 'g')"
+
     def digits_only(field_expr):
-        expr = Replace(field_expr, Value(" "), Value(""))
-        expr = Replace(expr, Value("-"), Value(""))
-        expr = Replace(expr, Value("."), Value(""))
-        expr = Replace(expr, Value("/"), Value(""))
-        expr = Replace(expr, Value("L"), Value(""))
-        return expr
+        return RegexpReplace(field_expr)
 
     lands = lands.extra(
         select={
             "verpachtungsgrad": "CASE WHEN groesse_qm > 0 THEN (verp_flaeche_aktuell / groesse_qm) * 100 ELSE 0 END"
         }
     ).annotate(
-        lfd_nr_num=Cast(NullIf(digits_only(F("lfd_nr")), Value("")), IntegerField()),
-        flur_num=Cast(NullIf(digits_only(F("flur")), Value("")), IntegerField()),
+        lfd_nr_num=Cast(NullIf(digits_only(F("lfd_nr")), Value("")), BigIntegerField()),
+        flur_num=Cast(NullIf(digits_only(F("flur")), Value("")), BigIntegerField()),
         flurstueck_num=Cast(
-            NullIf(digits_only(F("flurstueck")), Value("")), IntegerField()
+            NullIf(digits_only(F("flurstueck")), Value("")), BigIntegerField()
         ),
     )