ci: add custom runner images with Node.js pre-installed

k8s/infra/forgejo-runner-images/Dockerfile.golang

@@ -0,0 +1,12 @@
+FROM golang:1.26-bookworm
+
+# Add Node.js precheck script
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    nodejs npm \
+    && rm -rf /var/lib/apt/lists/*
+
+# Verify installations
+RUN node --version && npm --version && go version
+
+LABEL maintainer="homelab" \
+      description="Golang 1.26 + Node.js pre-installed with precheck"