Fix Paperless upload: handle async task UUID response

Paperless-ngx post_document returns a task UUID string, not a document
ID directly. The code assumed it was a dict and called .get() on a
string, causing AttributeError. Now polls the task status endpoint to
retrieve the actual integer document ID.

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

app/stiftung/tasks.py

@@ -28,6 +28,8 @@ import mimetypes
 from datetime import datetime, timezone as dt_timezone
 from email.header import decode_header, make_header
 
+import time
+
 import requests
 from celery import shared_task
 from django.conf import settings
@@ -84,6 +86,56 @@ def _get_email_body(msg) -> str:
     return "\n".join(body_parts).strip()
 
 
+def _poll_paperless_task(api_url: str, headers: dict, task_id: str, filename: str, max_wait: int = 120) -> int | None:
+    """
+    Pollt den Paperless-ngx Task-Status bis das Dokument verarbeitet wurde.
+    Gibt die Dokument-ID zurück, oder None bei Fehler/Timeout.
+    """
+    task_url = f"{api_url.rstrip('/')}/api/tasks/?task_id={task_id}"
+    waited = 0
+    interval = 2
+    while waited < max_wait:
+        try:
+            resp = requests.get(task_url, headers=headers, timeout=30)
+            resp.raise_for_status()
+            tasks = resp.json()
+            if tasks:
+                task = tasks[0] if isinstance(tasks, list) else tasks
+                status = task.get("status", "")
+                if status == "SUCCESS":
+                    related = task.get("related_document")
+                    if related:
+                        # related_document can be a URL like "/api/documents/42/"
+                        # or just an ID
+                        if isinstance(related, str):
+                            parts = related.rstrip("/").split("/")
+                            try:
+                                return int(parts[-1])
+                            except (ValueError, IndexError):
+                                logger.warning("Konnte Dokument-ID nicht aus '%s' extrahieren.", related)
+                                return None
+                        return int(related)
+                    # Some versions use result_id or document_id
+                    for key in ("result_id", "document_id", "id"):
+                        val = task.get(key)
+                        if val is not None:
+                            try:
+                                return int(val)
+                            except (ValueError, TypeError):
+                                pass
+                    logger.warning("Task %s erfolgreich aber keine Dokument-ID gefunden: %s", task_id, task)
+                    return None
+                elif status == "FAILURE":
+                    logger.error("Paperless-Task %s fehlgeschlagen für '%s': %s", task_id, filename, task.get("result"))
+                    return None
+        except requests.RequestException as exc:
+            logger.warning("Fehler beim Abfragen von Paperless-Task %s: %s", task_id, exc)
+        time.sleep(interval)
+        waited += interval
+    logger.error("Timeout beim Warten auf Paperless-Task %s für '%s' (%ds).", task_id, filename, max_wait)
+    return None
+
+
 def _upload_to_paperless(content: bytes, filename: str, destinataer=None, betreff: str = "") -> int | None:
     """
     Lädt einen Anhang in Paperless-NGX hoch.
@@ -140,9 +192,18 @@ def _upload_to_paperless(content: bytes, filename: str, destinataer=None, betref
             timeout=300,  # 5 Minuten für große Anhänge
         )
         response.raise_for_status()
-        # Paperless gibt die neue Dokument-ID zurück (als Integer oder UUID-String)
         result = response.json()
-        doc_id = result if isinstance(result, int) else result.get("id")
+
+        # Paperless-ngx post_document returns a task UUID string.
+        # We need to poll the task status to get the actual document ID.
+        if isinstance(result, str):
+            task_id = result
+            doc_id = _poll_paperless_task(api_url, headers, task_id, safe_filename)
+        elif isinstance(result, int):
+            doc_id = result
+        else:
+            doc_id = result.get("id")
+
         logger.info("Anhang '%s' erfolgreich in Paperless hochgeladen (ID: %s).", safe_filename, doc_id)
         return doc_id
     except requests.RequestException as exc: