I had a similar problem, except on a framework.

In my case worked for both commands

    npm run dev
    npm run build

I've tried to mirror my solution

=== src/index.js ===

    // file looks fine

    import "./styles/index.scss"

=== src/styles/index.scss ===

    .search-input {
        width: 100%;
        background-image: url("@iconsAlias/search.svg");
    }

=== vite.config.js ===

    import { defineConfig } from 'vite';
    import path from 'path';

    export default defineConfig({

        resolve: {

            alias: {

                '@iconsAlias': path.resolve(__dirname, 'src/assets/icons')

            }

        },

    });