Fix Docker build: use cp instead of mv to prevent directory collision

Dockerfile

@@ -25,8 +25,8 @@ RUN cd frontend && npm install && npm run build
 COPY --chown=user backend/ ./backend/
 COPY --chown=user codeblue_context.py .
 
-# Move built frontend to backend static directory
-RUN mv frontend/dist backend/static
+# Copy built frontend to backend static directory
+RUN rm -rf backend/static && mkdir -p backend/static && cp -r frontend/dist/* backend/static/
 
 # Set environment variables for Hugging Face
 ENV PORT=7860