refactor(docker): use Alpine system UID range, reference user by name

Drop explicit -u 1000/-g 1000 and let busybox assign from Alpine's
system UID range (100-999), aligning with -S (system account)
semantics. Reference the account by name in USER and --chown to
avoid hard-coding a numeric UID that could collide with future
Alpine releases or layered packages.

Dockerfile

@@ -7,7 +7,7 @@ RUN CGO_ENABLED=0 go build -a -installsuffix cgo -o deeplx .
 FROM alpine:latest
 WORKDIR /app
 RUN addgroup -S deeplx && adduser -h /app -G deeplx -SH deeplx
-USER deeplx
+USER deeplx:deeplx
-COPY --from=builder --chown=deeplx /go/src/github.com/OwO-Network/DeepLX/deeplx /app/deeplx
+COPY --from=builder --chown=deeplx:deeplx /go/src/github.com/OwO-Network/DeepLX/deeplx /app/deeplx
 EXPOSE 1188
 ENTRYPOINT ["/app/deeplx"]