Switch to dart-sass and make deploy script fail-safe

node-sass 4.x cannot build on arm64/Node 16. Use sass with ::v-deep
instead of /deep/, and only replace the server dist after the upload
is unpacked and verified.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

vue.config.js

@@ -25,6 +25,7 @@ module.exports = {
   css: {
     loaderOptions: {
       sass: {
+        implementation: require('sass'),
         data: `@import "@/assets/scss/base.scss";`
       }
     }