Fix indentation in Dockerfile for uv sync command

Author: huyuwei1996

backend/Dockerfile

@@ -14,8 +14,8 @@ ENV UV_PROJECT_ENVIRONMENT=/usr/local
 # Install dependencies
 RUN --mount=type=cache,target=/root/.cache/uv \
     --mount=type=bind,source=backend/uv.lock,target=uv.lock \
-	--mount=type=bind,source=backend/pyproject.toml,target=pyproject.toml \
-	uv sync --frozen --no-install-project --no-default-groups --group server
+    --mount=type=bind,source=backend/pyproject.toml,target=pyproject.toml \
+    uv sync --frozen --no-install-project --no-default-groups --group server
 
 
 FROM python:3.10-slim