Improve uv caching in Dockerfile

Author: dolfinus

docker/Dockerfile.backend

@@ -63,7 +63,9 @@ RUN --mount=type=cache,target=/root/.cache/uv \
         --link-mode copy \
         --no-install-project \
         --all-extras \
-        --compile-bytecode
+        --compile-bytecode \
+    && uv pip install pip \
+    && uv cache prune --ci
 
 
 FROM base AS prod
@@ -88,6 +90,7 @@ RUN --mount=type=cache,target=/root/.cache/uv \
         --no-install-project \
         --all-extras \
         --group "test" \
-        --compile-bytecode
+        --compile-bytecode \
+    && uv cache prune --ci
 
 RUN sed -i 's/python -m/coverage run -m/g' /app/docker/entrypoint.sh