Merge branch 'container/build-createuser'

Mirrors the telesrv-admin pattern - a static build stage compile, copied
into the final alpine image as /app/createuser - so the tool is
available wherever the server image runs, not just from a local go run.

Containerfile

@@ -18,12 +18,14 @@ RUN CGO_ENABLED=0 go build -trimpath \
     -ldflags "-X main.gitCommit=${GIT_COMMIT} -X main.gitBranch=${GIT_BRANCH} -X main.gitTreeState=${GIT_TREE_STATE} -X main.buildTime=${BUILD_TIME}" \
     -o /out/gramsrv ./cmd/telesrv
 RUN CGO_ENABLED=0 go build -trimpath -o /out/telesrv-admin ./cmd/telesrv-admin
+RUN CGO_ENABLED=0 go build -trimpath -o /out/createuser ./cmd/createuser
 
 FROM docker.io/library/alpine:3.20
 RUN apk add --no-cache ca-certificates tzdata ffmpeg
 WORKDIR /app
 COPY --from=build /out/gramsrv /app/gramsrv
 COPY --from=build /out/telesrv-admin /app/telesrv-admin
+COPY --from=build /out/createuser /app/createuser
 COPY --from=build /src/data/langpack /app/data/langpack
 COPY --from=build /src/data/sticker-seed /app/data/sticker-seed
 EXPOSE 2398 2600