fix: CAST statt ::jsonb in obligation_routes.py (SQLAlchemy-Kompatibilität)

SQLAlchemy interpretiert '::' als Parameter-Trenner — CAST(:param AS jsonb) verwenden.

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

backend-compliance/compliance/api/obligation_routes.py

@@ -201,7 +201,7 @@ async def create_obligation(
              status, priority, responsible, linked_systems, assessment_id, rule_code, notes)
         VALUES
             (:tenant_id, :title, :description, :source, :source_article, :deadline,
-             :status, :priority, :responsible, :linked_systems::jsonb, :assessment_id, :rule_code, :notes)
+             :status, :priority, :responsible, CAST(:linked_systems AS jsonb), :assessment_id, :rule_code, :notes)
         RETURNING *
     """), {
         "tenant_id": tenant_id,
@@ -255,7 +255,7 @@ async def update_obligation(
     for field, value in payload.model_dump(exclude_unset=True).items():
         if field == "linked_systems":
             updates["linked_systems"] = json.dumps(value or [])
-            set_clauses.append("linked_systems = :linked_systems::jsonb")
+            set_clauses.append("linked_systems = CAST(:linked_systems AS jsonb)")
         else:
             updates[field] = value
             set_clauses.append(f"{field} = :{field}")