feat: Email-Eingangsverarbeitung für Destinatäre implementieren

Neues System zur automatischen Verarbeitung eingehender E-Mails von
Destinatären. IMAP-Polling alle 15 Minuten via Celery Beat, automatische
Zuordnung zu Destinatären anhand der E-Mail-Adresse, Upload von Anhängen
zu Paperless-NGX.

Umfasst:
- DestinataerEmailEingang Model mit Status-Tracking
- Celery Task für IMAP-Polling und Paperless-Integration
- Web-UI (Liste + Detail) mit Such- und Filterfunktion
- Admin-Interface mit Bulk-Actions
- Agent-Dokumentation (SysAdmin, RentmeisterAI)
- Dev-Environment Modernisierung (docker compose v2)

Reviewed by: SysAdmin (STI-15), RentmeisterAI (STI-16)

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

compose.yml

@@ -57,6 +57,12 @@ services:
       - GRAMPS_USERNAME=${GRAMPS_USERNAME}
       - GRAMPS_PASSWORD=${GRAMPS_PASSWORD}
       - GRAMPS_API_TOKEN=${GRAMPS_API_TOKEN}
+      - IMAP_HOST=${IMAP_HOST}
+      - IMAP_PORT=${IMAP_PORT}
+      - IMAP_USER=${IMAP_USER}
+      - IMAP_PASSWORD=${IMAP_PASSWORD}
+      - IMAP_FOLDER=${IMAP_FOLDER}
+      - IMAP_USE_SSL=${IMAP_USE_SSL}
     ports:
       - "8081:8000"
     volumes:
@@ -78,6 +84,15 @@ services:
       - GRAMPS_USERNAME=${GRAMPS_USERNAME}
       - GRAMPS_PASSWORD=${GRAMPS_PASSWORD}
       - GRAMPS_API_TOKEN=${GRAMPS_API_TOKEN}
+      - IMAP_HOST=${IMAP_HOST}
+      - IMAP_PORT=${IMAP_PORT}
+      - IMAP_USER=${IMAP_USER}
+      - IMAP_PASSWORD=${IMAP_PASSWORD}
+      - IMAP_FOLDER=${IMAP_FOLDER}
+      - IMAP_USE_SSL=${IMAP_USE_SSL}
+      - PAPERLESS_API_URL=${PAPERLESS_API_URL}
+      - PAPERLESS_API_TOKEN=${PAPERLESS_API_TOKEN}
+      - PAPERLESS_DESTINATAERE_TAG_ID=${PAPERLESS_DESTINATAERE_TAG_ID}
     depends_on:
       - redis
       - db
@@ -98,6 +113,15 @@ services:
       - GRAMPS_USERNAME=${GRAMPS_USERNAME}
       - GRAMPS_PASSWORD=${GRAMPS_PASSWORD}
       - GRAMPS_API_TOKEN=${GRAMPS_API_TOKEN}
+      - IMAP_HOST=${IMAP_HOST}
+      - IMAP_PORT=${IMAP_PORT}
+      - IMAP_USER=${IMAP_USER}
+      - IMAP_PASSWORD=${IMAP_PASSWORD}
+      - IMAP_FOLDER=${IMAP_FOLDER}
+      - IMAP_USE_SSL=${IMAP_USE_SSL}
+      - PAPERLESS_API_URL=${PAPERLESS_API_URL}
+      - PAPERLESS_API_TOKEN=${PAPERLESS_API_TOKEN}
+      - PAPERLESS_DESTINATAERE_TAG_ID=${PAPERLESS_DESTINATAERE_TAG_ID}
     depends_on:
       - redis
       - db