Add BUILD_DATE arg for cache busting in Docker builds

Dockerfile

@@ -1,6 +1,10 @@
 # Build stage
 FROM node:20-alpine AS builder
 
+# Cache buster - wijzig BUILD_DATE in docker-compose om rebuild te forceren
+ARG BUILD_DATE=unknown
+RUN echo "Build date: $BUILD_DATE"
+
 # Install build dependencies for better-sqlite3
 RUN apk add --no-cache python3 make g++