feat: split flake into multiple hosts and add homelab config

hosts/lithium/services/uptime-kuma.nix

@@ -0,0 +1,18 @@
+{ config, pkgs, ... }:
+let
+  svcDomain = "status.${config.networking.domain}";
+  svcPort = config.services.uptime-kuma.settings.PORT;
+in
+{
+  services.caddy.virtualHosts."${svcDomain}".extraConfig = ''
+    reverse_proxy :${svcPort}
+  '';
+  # NOTE: Currently requires some web-interface configuration
+  # User must set up an admin account, monitors, and status pages manually.
+  services.uptime-kuma = {
+    enable = true;
+    # NOTE: NixOS Attributes here resolve into these ENV vars:
+    # https://github.com/louislam/uptime-kuma/wiki/Environment-Variables
+    # settings = {};
+  };
+}