Use maud for test page

I want to replace askama with maud completely. It's so much nicer to be
able to use Rust code and abstractions (e.g. functions) to compose HTML
than using a bespoke templating system with weird inheritance and stuff.
Even though said template system is checked at compile time. Actually,
since it doesn't do hot reloading anyways, maud requiring a recompile
for changes to become visible doesn't make the situation worse.

Cargo.toml

@@ -18,6 +18,7 @@ futures = "0.3.30"
 gethostname = "0.4.3"
 humantime = "2.1.0"
 log = "0.4.21"
+maud = { version = "0.26.0", features = ["axum"] }
 mime_guess = "2.0.4"
 open = "5.1.2"
 rand = "0.8.5"