feat: 服务端 promotion 视频自动转码；首页宣传册预览与 mp4 配置

Made-with: Cursor

server/Dockerfile

@@ -13,7 +13,8 @@ RUN CGO_ENABLED=0 go build -mod=vendor -o /app/server .
 ARG REGISTRY_MIRROR=docker.m.daocloud.io/library/
 FROM ${REGISTRY_MIRROR}alpine:3.19
 WORKDIR /app
-RUN apk add --no-cache ca-certificates tzdata
+# 产品视频 .mov → .mp4 服务端转码（handlers/promotion_transcode.go）
+RUN apk add --no-cache ca-certificates tzdata ffmpeg
 ENV TZ=Asia/Shanghai
 COPY --from=builder /app/server .
 EXPOSE 8088