mobile2: Casdoor OIDC auth deployment

- New branch for mobile2.falah-os.com with Casdoor OIDC
- Auth page with 'Sign in with Casdoor' button
- OIDC callback: exchanges code via server-side API route
- env vars configured on Netlify
- DNS auto-configured via Netlify (falah-os.com zone)

src/app/auth/page.tsx

@@ -3,9 +3,18 @@
 import { Suspense, useState, FormEvent, useEffect } from "react";
 import { useAuth } from "@/lib/AuthContext";
 import { useRouter, useSearchParams } from "next/navigation";
-import { Mail, ArrowLeft } from "lucide-react";
+import { Mail, ArrowLeft, Shield } from "lucide-react";
 import ErrorFeedback from "@/components/ErrorFeedback";
 
+const getCasdoorUrl = () => {
+  const state = Math.random().toString(36).slice(2, 10);
+  const base = process.env.NEXT_PUBLIC_CASDOOR_SERVER_URL || "https://auth.falahos.my";
+  const clientId = process.env.NEXT_PUBLIC_CASDOOR_CLIENT_ID || "272f91105da5cf984773";
+  const redirect = process.env.NEXT_PUBLIC_CASDOOR_REDIRECT_URI ||
+    "https://mobile2.falah-os.com/auth/callback";
+  return `${base}/login/oauth/authorize?client_id=${clientId}&redirect_uri=${encodeURIComponent(redirect)}&response_type=code&scope=openid+profile+email&state=${state}`;
+};
+
 type AuthMode = "login" | "register";
 type PageState = "select" | "email-form";
 
@@ -89,6 +98,22 @@ function AuthPageInner() {
 
           {/* Sign-in Methods */}
           <div className="space-y-3">
+            {/* Casdoor OIDC */}
+            <a
+              href={getCasdoorUrl()}
+              className="w-full flex items-center gap-4 px-5 py-4 rounded-2xl bg-green-900/20 border border-green-600/30 active:bg-green-900/30 transition-all touch-manipulation"
+            >
+              <div className="w-6 h-6 shrink-0 flex items-center justify-center">
+                <Shield size={22} className="text-green-400" />
+              </div>
+              <div className="text-left">
+                <span className="text-sm font-medium text-green-400 block">
+                  Sign in with Casdoor
+                </span>
+                <span className="text-xs text-gray-600">FalahOS Identity Service</span>
+              </div>
+            </a>
+
             {/* Email */}
             <button
               onClick={handleEmailClick}