Add IMAP configuration UI and sidebar navigation for email inbox

- Email settings page at /administration/email/ with IMAP config form
- Connection test button to verify IMAP connectivity
- Sidebar link "E-Mail Eingang" for quick access
- AppConfiguration model extended with email category and password type
- init_config command includes IMAP default settings
- DB-based IMAP config with env var fallback

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

app/stiftung/management/commands/init_config.py

@@ -91,10 +91,76 @@ class Command(BaseCommand):
             },
         ]
 
+        # E-Mail / IMAP Settings
+        email_settings = [
+            {
+                "key": "imap_host",
+                "display_name": "IMAP Server",
+                "description": "Hostname oder IP-Adresse des IMAP-Servers (z.B. mail.example.com)",
+                "value": "",
+                "default_value": "",
+                "setting_type": "text",
+                "category": "email",
+                "order": 1,
+            },
+            {
+                "key": "imap_port",
+                "display_name": "IMAP Port",
+                "description": "Port des IMAP-Servers (Standard: 993 für SSL, 143 für unverschlüsselt)",
+                "value": "993",
+                "default_value": "993",
+                "setting_type": "number",
+                "category": "email",
+                "order": 2,
+            },
+            {
+                "key": "imap_user",
+                "display_name": "IMAP Benutzername",
+                "description": "Benutzername / E-Mail-Adresse für die IMAP-Anmeldung",
+                "value": "",
+                "default_value": "",
+                "setting_type": "text",
+                "category": "email",
+                "order": 3,
+            },
+            {
+                "key": "imap_password",
+                "display_name": "IMAP Passwort",
+                "description": "Passwort für die IMAP-Anmeldung",
+                "value": "",
+                "default_value": "",
+                "setting_type": "password",
+                "category": "email",
+                "order": 4,
+            },
+            {
+                "key": "imap_folder",
+                "display_name": "IMAP Ordner",
+                "description": "Name des zu überwachenden Postfach-Ordners (Standard: INBOX)",
+                "value": "INBOX",
+                "default_value": "INBOX",
+                "setting_type": "text",
+                "category": "email",
+                "order": 5,
+            },
+            {
+                "key": "imap_use_ssl",
+                "display_name": "SSL/TLS verwenden",
+                "description": "Sichere Verbindung zum IMAP-Server (empfohlen)",
+                "value": "True",
+                "default_value": "True",
+                "setting_type": "boolean",
+                "category": "email",
+                "order": 6,
+            },
+        ]
+
+        all_settings = paperless_settings + email_settings
+
         created_count = 0
         updated_count = 0
 
-        for setting_data in paperless_settings:
+        for setting_data in all_settings:
             setting, created = AppConfiguration.objects.get_or_create(
                 key=setting_data["key"], defaults=setting_data
             )

app/stiftung/models/system.py

@@ -313,6 +313,7 @@ class AppConfiguration(models.Model):
 
     SETTING_TYPE_CHOICES = [
         ("text", "Text"),
+        ("password", "Password"),
         ("number", "Number"),
         ("boolean", "Boolean"),
         ("url", "URL"),
@@ -322,6 +323,7 @@ class AppConfiguration(models.Model):
 
     CATEGORY_CHOICES = [
         ("paperless", "Paperless Integration"),
+        ("email", "E-Mail / IMAP"),
         ("general", "General Settings"),
         ("corporate", "Corporate Identity"),
         ("notifications", "Notifications"),

app/stiftung/urls.py

@@ -262,6 +262,7 @@ urlpatterns = [
     # Administration URLs
     path("administration/", views.administration, name="administration"),
     path("administration/settings/", views.app_settings, name="app_settings"),
+    path("administration/email/", views.email_settings, name="email_settings"),
     path("administration/audit-log/", views.audit_log_list, name="audit_log_list"),
     path("administration/backup/", views.backup_management, name="backup_management"),
     path(

app/stiftung/views/__init__.py

@@ -156,6 +156,7 @@ from .system import (  # noqa: F401
     user_login,
     user_logout,
     app_settings,
+    email_settings,
     edit_help_box,
     two_factor_setup,
     two_factor_qr,