fix: use Go 1.25.5 with custom Docker build stage

Download Go 1.25.5 directly in Dockerfile since official images don't exist yet.

Dockerfile

@@ -1,8 +1,25 @@
-# Build stage
-FROM golang:1.23.4-bookworm AS builder
+# Build stage - Install Go 1.25.5 from source
+FROM debian:bookworm-slim AS go-installer
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    git make gcc libc6-dev bash \
+    wget ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+ARG GO_VERSION=1.25.5
+ARG TARGETARCH
+
+RUN wget -q "https://go.dev/dl/go${GO_VERSION}.linux-${TARGETARCH}.tar.gz" \
+    && tar -C /usr/local -xzf "go${GO_VERSION}.linux-${TARGETARCH}.tar.gz" \
+    && rm "go${GO_VERSION}.linux-${TARGETARCH}.tar.gz"
+
+# Build stage
+FROM debian:bookworm-slim AS builder
+
+COPY --from=go-installer /usr/local/go /usr/local/go
+ENV PATH="/usr/local/go/bin:${PATH}"
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    git make gcc libc6-dev \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /build
@@ -37,4 +54,4 @@ USER netrunner
 
 EXPOSE 8080 8081
 
-ENTRYPOINT ["/usr/local/bin/netrunner"]
+ENTRYPOINT ["/usr/local/bin/netrunner"]

go.mod

@@ -1,6 +1,6 @@
 module github.com/luxfi/netrunner
 
-go 1.23.4
+go 1.25.5
 
 exclude google.golang.org/genproto v0.0.0-20230410155749-daa745c078e1