feat: split flake into multiple hosts and add homelab config

hosts/lithium/services/caddy.nix

@@ -0,0 +1,41 @@
+{ config, pkgs, ... }:
+{
+  sops.secrets.caddy_env = {
+    sopsFile = ../secrets/caddy.env;
+    format = "dotenv";
+    mode = "0440";
+    owner = config.services.caddy.user;
+    group = config.services.caddy.group;
+    restartUnits = [ "caddy.service" ];
+  };
+  services.caddy = {
+    enable = true;
+    package = pkgs.caddy.withPlugins {
+      # NOTE: Occasionally specify @latest and update the new versions, and the result hash.
+      plugins = [
+        "github.com/mholt/caddy-dynamicdns@v0.0.0-20250430031602-b846b9e8fb83"
+        "github.com/caddy-dns/cloudflare@v0.2.1"
+      ];
+
+      # NOTE: Built on 6/4/2025
+      hash = "sha256-swskhAr7yFJX+qy0FR54nqJarTOojwhV2Mbk7+fyS0I=";
+    };
+    # NOTE: Use Staging CA while testing, check `systemctl status caddy`
+    # to see if everything is working.
+    # acmeCA = "https://acme-staging-v02.api.letsencrypt.org/directory";
+
+    # TODO: Add Metrics with Prometheus & Grafana
+    environmentFile = config.sops.secrets.caddy_env.path;
+    globalConfig = ''
+      # acme_dns cloudflare {env.CLOUDFLARE_API_TOKEN}
+      dynamic_dns {
+        provider cloudflare {env.CLOUDFLARE_API_TOKEN}
+        domains {
+          ${config.networking.domain} @
+        }
+        dynamic_domains
+      }
+    '';
+  };
+  networking.firewall.allowedTCPPorts = [ 80 443 ];
+}