manatee: Add services homepage with auto-discovery

Add a homepage module that generates a static landing page served on
port 9999 via nginx. Each service module registers itself via the shared
mod.homepage.services option, so enabling a module automatically adds
it to the page.

hosts/manatee/modules/home-assistant/default.nix

@@ -62,6 +62,12 @@ let
   '';
 in
 {
+  mod.homepage.services = [{
+    name = "Home Assistant";
+    port = 8123;
+    description = "Home automation";
+  }];
+
   hardware.bluetooth.enable = true;
 
   virtualisation.oci-containers = {