Fix missing OIDC button: stop static-prerendering /login

/login was prerendered at Docker build time when AUTH_OIDC_* were
unset, baking oidcEnabled=false into the page. Force dynamic render
and also read /api/v1/auth/config on the client as a fallback.

src/app/login/page.tsx

@@ -1,6 +1,10 @@
 import { isOidcConfigured } from "@/lib/auth/oidc";
 import { LoginPageClient } from "@/components/LoginPageClient";
 
+// OIDC env is only available at runtime (Docker). Never prerender this page
+// at build time or the SSO button stays permanently hidden.
+export const dynamic = "force-dynamic";
+
 export default function LoginPage() {
   const authUrl = (process.env.AUTH_URL || "").replace(/\/$/, "");
   const callbackUrlHint = authUrl

src/components/LoginPageClient.tsx

@@ -1,6 +1,6 @@
 "use client";
 
-import { FormEvent, useState } from "react";
+import { FormEvent, useEffect, useState } from "react";
 import { signIn } from "next-auth/react";
 import { useRouter, useSearchParams } from "next/navigation";
 import { Suspense } from "react";
@@ -11,6 +11,12 @@ type Props = {
   callbackUrlHint: string;
 };
 
+type AuthConfig = {
+  oidcEnabled: boolean;
+  oidcName: string;
+  callbackUrl: string;
+};
+
 function authErrorMessage(code: string | null): string | null {
   if (!code) return null;
   switch (code) {
@@ -40,6 +46,23 @@ function LoginForm({ oidcEnabled, oidcName, callbackUrlHint }: Props) {
     authErrorMessage(params.get("error"))
   );
   const [loading, setLoading] = useState(false);
+  const [runtimeOidc, setRuntimeOidc] = useState<AuthConfig | null>(null);
+
+  // Belt-and-suspenders: ask the live API so a stale static shell can't hide SSO
+  useEffect(() => {
+    fetch("/api/v1/auth/config")
+      .then((r) => (r.ok ? r.json() : null))
+      .then((data: AuthConfig | null) => {
+        if (data) setRuntimeOidc(data);
+      })
+      .catch(() => {
+        /* ignore */
+      });
+  }, []);
+
+  const showOidc = runtimeOidc?.oidcEnabled ?? oidcEnabled;
+  const displayName = runtimeOidc?.oidcName || oidcName;
+  const redirectHint = runtimeOidc?.callbackUrl || callbackUrlHint;
 
   async function onSubmit(e: FormEvent) {
     e.preventDefault();
@@ -97,19 +120,19 @@ function LoginForm({ oidcEnabled, oidcName, callbackUrlHint }: Props) {
         <button className="btn" type="submit" disabled={loading}>
           {loading ? "Signing in…" : "Sign in"}
         </button>
-        {oidcEnabled && (
+        {showOidc && (
           <>
             <button
               type="button"
               className="btn btn-secondary"
               onClick={() => signIn("oidc", { callbackUrl })}
             >
-              Sign in with {oidcName}
+              Sign in with {displayName}
             </button>
             <p className="muted" style={{ margin: 0, fontSize: "0.75rem" }}>
               IdP redirect URI must be exactly:
               <br />
-              <code className="mono">{callbackUrlHint}</code>
+              <code className="mono">{redirectHint}</code>
             </p>
           </>
         )}