admin-console: fix duplicate package main, fix Dockerfile build order

admin-console/Dockerfile

@@ -1,8 +1,7 @@
 FROM golang:1.26-alpine AS builder
 WORKDIR /build
-COPY go.mod ./
-RUN go mod tidy
 COPY . .
+RUN go mod tidy
 RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags="-s -w" -o admin-console ./cmd/server/
 
 FROM alpine:3.20

admin-console/cmd/server/main.go

@@ -1,5 +1,4 @@
 package main
-package main
 
 import (
 	"log"