refactor: remove db module from Dockerfile and consolidate dependencies

- Removed the db module from the Dockerfile, reflecting the recent refactor that consolidates database functionality into the core/mongo package.
- This change simplifies the Docker image setup by eliminating unnecessary dependencies and improving overall project organization.

backend/Dockerfile

@@ -9,7 +9,6 @@ COPY ./backend ./backend/
 
 # Copy required modules from relative paths
 COPY ./core ./core/
-COPY ./db ./db/
 COPY ./grpc ./grpc/
 COPY ./trace ./trace/
 COPY ./vcs ./vcs/