Fixed bug in Dockerfile

Dockerfile

@@ -54,4 +54,4 @@ HEALTHCHECK --interval=30s --timeout=10s --start-period=10s --retries=3 \
 # Run the application
 # Use standard asyncio loop (uvloop has permission issues in some Docker environments)
 # Port is configurable via PORT environment variable (default: 8000)
-CMD sh -c "uvicorn backend.app.main:app --host 0.0.0.0 --port ${PORT:-8000} --loop asyncio"
+CMD ["sh", "-c", "uvicorn backend.app.main:app --host 0.0.0.0 --port ${PORT:-8000} --loop asyncio"]