feat: add knowledge retrieval service

backend/apps/solutions/api.py

@@ -20,7 +20,7 @@ router = Router(tags=["solutions"])
 @router.post("", response=SolutionOut)
 def create_solution(request, payload: SolutionIn):
     require_permission(request, "solution.manage")
-    return Solution.objects.create(
+    solution = Solution.objects.create(
         title=payload.title,
         problem_signature=payload.problem_signature,
         related_system=payload.related_system,
@@ -31,6 +31,11 @@ def create_solution(request, payload: SolutionIn):
         status=payload.status,
         created_by=request.user if request.user.is_authenticated else None,
     )
+    if solution.status == "published":
+        from apps.knowledge.services import index_published_solution
+
+        index_published_solution(solution)
+    return solution
 
 
 @router.get("", response=list[SolutionOut])