Add deprecation warnings to all clanModules

clanModules/sshd/roles/server.nix

@@ -17,6 +17,13 @@ in
     clan.sshd.hostKeys.rsa.enable = lib.mkEnableOption "Generate RSA host key";
   };
   config = {
+
+    warnings = [
+      "The clan.sshd module is deprecated and will be removed on 2025-07-15.
+      Please migrate to user-maintained configuration or the new equivalent clan services
+      (https://docs.clan.lol/reference/clanServices)."
+    ];
+
     services.openssh = {
       enable = true;
       settings.PasswordAuthentication = false;