Fix Syncfusion license configuration

[chrispaulintheory]

Load the Syncfusion license key from the project-local environment file instead of using the hardcoded placeholder.

[chrispaulintheory]

The .env file is here "src/Quickfire.Blazor/.env" and so I needed to be clear about the path with:

Env.Load(Path.Combine(builder.Environment.ContentRootPath, ".env"));

Also, Env.Load() may overwrite a production value with the .env value. Env.NoClobber().Load() preserves the production value and if no value already exists, it will load the value from .env normally. This gives deployment/server configuration priority while still supporting local .env.