Pull Seq address from configuration

Right now, in Program.cs, we're creating a log sink to Seq, but the URL is hard-coded to a localhost URL. We should be a bit more flexible there and pull from config.

Start in Program.cs, where the Seq log sink is created with a hard-coded localhost URL. Inspect how this application loads configuration and determine where the Seq URL should come from. Done means the sink no longer depends on that hard-coded URL and can use the configured value; no tests or configuration files are named in the issue.

Written by the indexing model from the issue text.