fix: enforce GOTOOLCHAIN=local in dockerfile

Dockerfile

@@ -1,8 +1,10 @@
 # ---- Backend Builder ----
 FROM golang:1.24-alpine AS backend-builder
+ENV GOTOOLCHAIN=local
 WORKDIR /app
 RUN apk add --no-cache git gcc musl-dev
 COPY backend/go.mod backend/go.sum ./
+RUN (echo "module kvtube-go"; echo ""; echo "go 1.24.0"; tail -n +4 go.mod) > go.mod.new && mv go.mod.new go.mod && go mod tidy
 RUN go mod download
 COPY backend/ ./
 RUN CGO_ENABLED=1 GOOS=linux GOARCH=amd64 go build -o kv-tube .
@@ -26,15 +28,14 @@ RUN echo "NEXT_PUBLIC_API_URL=$NEXT_PUBLIC_API_URL" && npm run build
 FROM alpine:latest
 
 # Install dependencies for Go backend, Node.js frontend, and Supervisord
-RUN apk add --no-cache \
-    nodejs \
-    ca-certificates \
-    ffmpeg \
-    curl \
-    python3 \
-    py3-pip \
-    supervisor \
-    && curl -L https://github.com/yt-dlp/yt-dlp/releases/latest/download/yt-dlp -o /usr/local/bin/yt-dlp \
+RUN apk add --no-cache nodejs
+RUN apk add --no-cache ca-certificates
+RUN apk add --no-cache ffmpeg
+RUN apk add --no-cache curl
+RUN apk add --no-cache python3
+RUN apk add --no-cache py3-pip
+RUN apk add --no-cache supervisor
+RUN curl -L https://github.com/yt-dlp/yt-dlp/releases/latest/download/yt-dlp -o /usr/local/bin/yt-dlp \
     && chmod a+rx /usr/local/bin/yt-dlp
 
 WORKDIR /app

backend/go.mod

@@ -1,6 +1,6 @@
 module kvtube-go
 
-go 1.25.0
+go 1.24.0
 
 require (
 	github.com/gin-gonic/gin v1.11.0