Fix maintenance redirects and admin host detection

tests/admin-routing.test.ts

@@ -0,0 +1,17 @@
+import { describe, expect, it } from "vitest";
+
+import { getRequestHostname } from "../lib/admin-routing";
+
+describe("admin routing helpers", () => {
+  it("prefers the first non-empty forwarded hostname", () => {
+    expect(getRequestHostname("root.mohfarawati.de", "internal-service")).toBe("root.mohfarawati.de");
+  });
+
+  it("normalizes ports and comma-separated proxy values", () => {
+    expect(getRequestHostname(undefined, "root.mohfarawati.de:443, proxy")).toBe("root.mohfarawati.de");
+  });
+
+  it("falls back to an empty string when no hostname exists", () => {
+    expect(getRequestHostname(undefined, null, "")).toBe("");
+  });
+});