fix(i-c): BUG-036 behoben — Workflow-Instances GET lieferte 500 auf jeden Aufruf (Route übergab user_id/is_system_admin die die Service-Signatur nicht akzeptierte → TypeError); Service um optionale User-Filterung erweitert (Nicht-Admins sehen nur eigene Instanzen via initiated_by, Admins alle); Beweistest test_bug036_instances.py 2/2 grün

app/services/workflow_service.py

@@ -401,14 +401,25 @@ async def list_instances(
     page: int = 1,
     page_size: int = 20,
     status_filter: str | None = None,
+    user_id: uuid.UUID | None = None,
+    is_system_admin: bool = False,
 ) -> dict[str, Any]:
-    """List workflow instances with optional status filter."""
+    """List workflow instances with optional status filter.
+
+    BUG-036 fix: the route passed ``user_id``/``is_system_admin`` which this
+    signature did not accept -> TypeError -> 500 on every call.
+
+    Non-admin users see only instances they initiated; admins/system admins
+    see all instances of the tenant.
+    """
     page = max(1, page)
     page_size = max(1, min(100, page_size))
 
     base = select(WorkflowInstance).where(WorkflowInstance.tenant_id == tenant_id)
     if status_filter:
         base = base.where(WorkflowInstance.status == status_filter)
+    if not is_system_admin and user_id is not None:
+        base = base.where(WorkflowInstance.initiated_by == user_id)
 
     count_q = select(func.count()).select_from(base.subquery())
     total_result = await db.execute(count_q)