fix(deploy): keep BuildKit cache and use Huawei mirrors for API images

Gitea run 2828 validated, then publish hit the 60-minute deadline while
Aliyun apt/pip crawled at about 22 kB/s after a 72h cache prune on a
runner with 677 GiB free. Skip BuildKit prune when disk is above the
minimum, split API apt/pip layers, and point apt/pypi at Huawei Cloud.

deploy/railway-api.Dockerfile

@@ -2,15 +2,18 @@ FROM swr.cn-north-4.myhuaweicloud.com/ddn-k8s/docker.io/library/python:3.12-slim
 
 ENV PYTHONUNBUFFERED=1 \
     PIP_NO_CACHE_DIR=1 \
-    PIP_INDEX_URL=https://mirrors.aliyun.com/pypi/simple/ \
+    PIP_INDEX_URL=https://mirrors.huaweicloud.com/repository/pypi/simple/ \
     PIP_DEFAULT_TIMEOUT=60
 WORKDIR /app
 
 COPY requirements.txt deploy/patch_vedastro_update_check.py ./
-RUN sed -i 's|http://deb.debian.org|https://mirrors.aliyun.com|g' /etc/apt/sources.list.d/debian.sources \
+# Apt packages are their own layer so a later pip timeout can reuse them.
+# Huawei mirrors share the SWR path already used for the base image; Aliyun
+# debian/pypi at ~22 kB/s cannot finish this RUN inside the 60-minute publish job.
+RUN sed -i 's|http://deb.debian.org|https://mirrors.huaweicloud.com|g' /etc/apt/sources.list.d/debian.sources \
     && apt-get -o Acquire::Retries=3 -o Acquire::http::Timeout=30 -o Acquire::https::Timeout=30 update \
-    && apt-get install -y --no-install-recommends build-essential nodejs \
-    && python -m pip install -r requirements.txt \
+    && apt-get install -y --no-install-recommends build-essential nodejs
+RUN python -m pip install -r requirements.txt \
     && python patch_vedastro_update_check.py \
     && apt-get purge -y --auto-remove build-essential \
     && rm -rf /var/lib/apt/lists/*