Deny all robots

Currently the robots.txt is set up to allow complete access by robots.
This means that well meaning bots that actually respect a sites wishes
with regards to crawling will be invited into the maze.

I think it makes more sense to tell all robots to go away, and if the
robot just blindly ignores this it will get lost in the babble tarpit.

Given enough babble instances this means that over time bot creators
will write LLM scraping bots that respect robots.txt so that they don't
incur the cost to their compute, bandwidth, and ultimately the quality
of their model.

```
To exclude all robots from the entire server

User-agent: *
Disallow: /

To allow all robots complete access

User-agent: *
Disallow:
```

via https://www.robotstxt.org/robotstxt.html

src/robots.txt

@@ -1,2 +1,2 @@
 User-agent: *
-Disallow:
+Disallow: /