fix: RAG service Dockerfile path patch

[bangqipropel]

Reason for Change:
Docker file path fixed

Requirements

• added unit tests and e2e tests (if applicable).

Issue Fixed:
if we don't name the path as ragengine, it will report the following error:

Traceback (most recent call last):
  File "/app/services/main.py", line 5, in <module>
    from vector_store_manager.manager import VectorStoreManager
  File "/app/services/vector_store_manager/manager.py", line 6, in <module>
    from ragengine.models import Document
ModuleNotFoundError: No module named 'ragengine'

Notes for Reviewers: