Fix template selection

[senko]

Three fixes:

1. make it clearer to GPT that it should not select a template if the tech is different (and special-casing react here because it seems to always be selected for "plain html/css" projects)
2. for react+express template, if the user visits http://localhost:3000/ we want to redirect to the vite dev server in development (and only serve frontend built with "npm run build:ui" if we have it, which usually won't be the case in development)
3. On older versionos of Node, import.meta.dirname is not defined, so use a fallback method to determine the dist folder