build: propagate VERSION into frontend build (VITE_APP_VERSION)

Dockerfile

@@ -31,6 +31,11 @@ WORKDIR /app/frontend
 # Copy frontend package files
 COPY frontend/package*.json ./
 
+# Build-time project version (propagated from top-level build-arg)
+ARG VERSION=dev
+# Make version available to Vite as VITE_APP_VERSION during the frontend build
+ENV VITE_APP_VERSION=${VERSION}
+
 # Set environment to bypass native binary requirement for cross-arch builds
 ENV npm_config_rollup_skip_nodejs_native=1 \
     ROLLUP_SKIP_NODEJS_NATIVE=1