fix(docker): keep /sbin in PATH so apk works during image build

Dockerfile.standalone

@@ -19,11 +19,12 @@ RUN CGO_ENABLED=0 GOOS=linux go build -o /taskpool .
 # Production stage
 FROM alpine:3.19
 
+# 注意：PATH 必须保留 /sbin:/usr/sbin，否则 alpine 的 apk 找不到
 ENV TZ=Asia/Shanghai \
     MISE_DATA_DIR=/app/envs/mise \
     MISE_CONFIG_DIR=/app/envs/mise \
     MISE_HIDE_UPDATE_WARNING=1 \
-    PATH="/app/envs/mise/shims:/app/envs/mise/bin:/usr/local/bin:/usr/bin:/bin"
+    PATH="/app/envs/mise/shims:/app/envs/mise/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
 
 RUN apk add --no-cache \
       nginx supervisor bash curl wget ca-certificates tzdata git rsync openssh-client \