Deploy MQTT test backend with private viewer and Gitea CI/CD

Dockerfile

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+FROM golang:1.27.1-alpine AS build
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /out/test-mqtt5 ./cmd/test-mqtt5 \
+    && CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /out/device-sim ./cmd/device-sim
+
+FROM build AS test
+RUN go test ./... && go vet ./...
+
+FROM alpine:3.22
+RUN addgroup -S -g 10001 app && adduser -S -D -H -u 10001 -G app app \
+    && apk add --no-cache ca-certificates
+COPY --from=build /out/test-mqtt5 /test-mqtt5
+COPY --from=build /out/device-sim /device-sim
+USER app:app
+ENTRYPOINT ["/test-mqtt5"]