Add option to serve CSS/JS libraries locally instead of via CDN

[palves-ulht]

Is your feature request related to a problem? Please describe.
Right now, the HTML pages depend on CSS and JS libraries hosted on external CDNs. This causes issues in constrained environments (e.g., school or corporate computers) where internet access is restricted, and only a limited set of URLs (such as this server) are accessible. As a result, the application may not render or function correctly in those environments.

Describe the solution you'd like
I would like an admin-configurable setting that allows these libraries to be served locally from the same server, instead of always pulling them from a CDN. This would ensure the application remains functional even in restricted-network setups.

Describe alternatives you've considered
Whitelisting CDN URLs, but this is often not feasible in constrained student or enterprise environments.