feat(sgx): add Uptime Kuma to monitor mx services independently

Runs on sgx so alerts (via Gmail) still work even if mx is down.
Available at https://status.hoyer.world behind nginx with ACME cert.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

systems/x86_64-linux/sgx/acme.nix

@@ -15,6 +15,7 @@
         "openwebui.hoyer.world"
         "syncthing.hoyer.world"
         "home.hoyer.world"
+        "status.hoyer.world"
       ];
     };
   };

systems/x86_64-linux/sgx/default.nix

@@ -11,6 +11,7 @@
     ./mail.nix
     ./wyoming.nix
     ./searx.nix
+    ./uptime-kuma.nix
   ];
 
   boot.tmp.useTmpfs = false;

systems/x86_64-linux/sgx/nginx.nix

@@ -32,5 +32,14 @@
         proxyWebsockets = true;
       };
     };
+    "status.hoyer.world" = {
+      enableACME = false;
+      useACMEHost = "internal.hoyer.world";
+      forceSSL = true;
+      locations."/" = {
+        proxyPass = "http://127.0.0.1:4000";
+        proxyWebsockets = true;
+      };
+    };
   };
 }

systems/x86_64-linux/sgx/uptime-kuma.nix

@@ -0,0 +1,10 @@
+{ ... }:
+{
+  services.uptime-kuma = {
+    enable = true;
+    settings = {
+      PORT = "4000";
+      HOST = "127.0.0.1";
+    };
+  };
+}