Update frequency: Re-crawl SCC calendar every 30 minutes; only do a deep crawl if something changes

[davepeck]

At the moment, I've configured a GitHub Action to crawl the SCC calendar once a day (at 12:30AM) and, if there is new content, extract & summarize + deploy to https://scc.frontseat.org/

This isn't good enough. Today, a couple meetings got added in the middle of the day. I'd like summaries to show up as soon as possible.

For this task, we will:

• Update the ./engage legistar crawl-calendar command to support a new --deep flag. If this flag is provided, we'll do what we currently do: crawl Calendar.aspx and everything it links to. However, if --deep is not provided, we'll only look at Calendar.aspx itself. Unless it has materially changed, we won't proceed with a full crawl and will exit with a special status. Our update script will see this status and decide no further summarization work is needed.
• Add a deployment pass directly to our update pass; if we update, then we deploy. Currently these are separated (aka our update action happens at 12:30AM and our deploy at 2:30AM to leave time for the update to finish).