feat: 交付官方 Docker 运行时，外观改背景图并下线自定义 CSS/JS

站点/后台分轨背景与用户列表排序一并落地；生产 CORS 改走 SITE_URL，健康检查带版本号。

Co-authored-by: Cursor <cursoragent@cursor.com>

deploy/Dockerfile.api

@@ -0,0 +1,32 @@
+# 构建上下文：仓库根。不含源码与工具链。
+# syntax=docker/dockerfile:1
+
+FROM golang:1.27-bookworm AS build
+WORKDIR /src
+ENV GOTOOLCHAIN=local
+COPY backend/go.mod backend/go.sum ./
+RUN go mod download
+COPY backend/ ./
+ARG VERSION=dev
+ARG COMMIT=unknown
+RUN CGO_ENABLED=0 GOOS=linux go build \
+    -trimpath \
+    -ldflags="-s -w -X github.com/freefire/jiang13-bbs/version.Version=${VERSION} -X github.com/freefire/jiang13-bbs/version.Commit=${COMMIT}" \
+    -o /out/jiang13 ./cmd/jiang13
+
+FROM alpine:3.21
+RUN apk add --no-cache ca-certificates tzdata wget su-exec \
+    && adduser -D -H -u 1000 jiang13 \
+    && mkdir -p /var/lib/jiang13/data
+COPY --from=build /out/jiang13 /usr/local/bin/jiang13
+COPY deploy/api-entrypoint.sh /usr/local/bin/api-entrypoint.sh
+RUN sed -i 's/\r$//' /usr/local/bin/api-entrypoint.sh && chmod +x /usr/local/bin/api-entrypoint.sh
+ENV JIANG13_WORK_PATH=/var/lib/jiang13 \
+    HTTP_PORT=3001 \
+    DEV_MODE=false \
+    TZ=UTC
+WORKDIR /var/lib/jiang13
+EXPOSE 3001
+HEALTHCHECK --interval=10s --timeout=3s --start-period=20s --retries=5 \
+    CMD wget -qO- http://127.0.0.1:3001/health || exit 1
+ENTRYPOINT ["/usr/local/bin/api-entrypoint.sh"]