feat: adding combined dockerfile for testing phase

combined/Dockerfile.multistage

@@ -0,0 +1,25 @@
+FROM golang:1.25-bookworm AS builder
+WORKDIR /app
+
+# Install build dependencies
+RUN apt-get update && apt-get install -y gcc libc6-dev git && rm -rf /var/lib/apt/lists/*
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+# Build with version info from git (matching goreleaser ldflags)
+RUN CGO_ENABLED=1 GOOS=linux go build \
+    -ldflags="-s -w \
+    -X github.com/netbirdio/netbird/version.version=$(git describe --tags --always --dirty 2>/dev/null || echo 'dev') \
+    -X main.commit=$(git rev-parse --short HEAD 2>/dev/null || echo 'unknown') \
+    -X main.date=$(date -u +%Y-%m-%dT%H:%M:%SZ) \
+    -X main.builtBy=docker" \
+    -o netbird-server ./combined
+
+FROM ubuntu:24.04
+RUN apt update && apt install -y ca-certificates && rm -fr /var/cache/apt
+ENTRYPOINT [ "/go/bin/netbird-server" ]
+CMD ["--config", "/etc/netbird/config.yaml"]
+COPY --from=builder /app/netbird-server /go/bin/netbird-server