feat: surface Google SSO on the login page

backend/src/main/java/com/dbaagent/controller/SetupController.java

@@ -6,6 +6,7 @@
 import com.dbaagent.service.SystemConfigService;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import org.springframework.beans.factory.annotation.Value;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
 import org.springframework.web.client.RestClient;
@@ -34,6 +35,17 @@ public class SetupController {
     private final CredentialRepository credentialRepository;
     private final LlmConfigResolver llmConfigResolver;
 
+    /**
+     * Mirrors {@code security.google.enabled}. Surfaced on the public status
+     * endpoint so the login page can decide whether to offer Google sign-in —
+     * it is otherwise unauthenticated and has no way to know the server was
+     * configured for SSO. Deliberately NOT final: {@code @RequiredArgsConstructor}
+     * would pull a final field into the constructor and Spring has no bean to
+     * satisfy it.
+     */
+    @Value("${security.google.enabled:false}")
+    private boolean googleEnabled;
+
     // ── GET /setup/status ─────────────────────────────────────────────────────
 
     /** Returns setup completion state. Public endpoint — no auth required. */
@@ -53,7 +65,8 @@ public SetupStatusResponse getStatus() {
                 setupComplete,
                 hasOrgInfo,
                 hasConnections,
-                hasLlmConfig
+                hasLlmConfig,
+                googleEnabled
         );
     }
 
@@ -278,7 +291,9 @@ public record SetupStatusResponse(
             boolean setupComplete,
             boolean hasOrganizationInfo,
             boolean hasConnections,
-            boolean hasLlmConfig
+            boolean hasLlmConfig,
+            /** Whether Google Workspace SSO is configured; drives the login page's SSO button. */
+            boolean googleEnabled
     ) {}
 
     public record InitializeRequest(String orgName, String adminUsername, String adminEmail, String adminPassword) {}

src/pages/Login.jsx

@@ -99,6 +99,7 @@ export default function Login() {
 
 
   const renderLoginStep = () => (
+    <>
     <form onSubmit={handlePasswordLogin} className="space-y-5">
       <div>
         <label htmlFor="email" className="text-xs font-semibold text-gray-500 uppercase tracking-wider block mb-1.5">
@@ -147,6 +148,44 @@ export default function Login() {
         {loading ? 'Signing in…' : 'Sign In'}
       </button>
     </form>
+
+    {/*
+      Only rendered when the server reports security.google.enabled. The login
+      page is unauthenticated, so /setup/status (already public, already fetched
+      above) is how it learns SSO exists — otherwise this button would 500 for
+      every install that never configured Google.
+
+      A plain <a>, not a button: /api/auth/google/start issues a 302 to Google,
+      so this is a full-page navigation and must not submit the form above.
+    */}
+    {setupStatus?.googleEnabled && (
+      <div className="mt-6">
+        <div className="relative">
+          <div className="absolute inset-0 flex items-center" aria-hidden="true">
+            <div className="w-full border-t border-gray-200" />
+          </div>
+          <div className="relative flex justify-center">
+            <span className="bg-white px-3 text-xs font-medium uppercase tracking-wider text-gray-400">
+              or
+            </span>
+          </div>
+        </div>
+
+        <a
+          href={authAPI.getGoogleStartUrl()}
+          className="mt-6 w-full min-h-[48px] flex items-center justify-center gap-3 bg-white border border-gray-300 hover:bg-gray-50 text-gray-700 font-semibold py-3 rounded-full shadow-sm transition-all active:scale-[0.98]"
+        >
+          <svg className="h-5 w-5" viewBox="0 0 24 24" aria-hidden="true">
+            <path fill="#4285F4" d="M22.56 12.25c0-.78-.07-1.53-.2-2.25H12v4.26h5.92a5.06 5.06 0 0 1-2.2 3.32v2.76h3.57c2.08-1.92 3.28-4.74 3.28-8.09z" />
+            <path fill="#34A853" d="M12 23c2.97 0 5.46-.98 7.28-2.66l-3.57-2.76c-.98.66-2.23 1.06-3.71 1.06-2.86 0-5.29-1.93-6.16-4.53H2.18v2.84A11 11 0 0 0 12 23z" />
+            <path fill="#FBBC05" d="M5.84 14.11a6.6 6.6 0 0 1 0-4.22V7.05H2.18a11 11 0 0 0 0 9.9l3.66-2.84z" />
+            <path fill="#EA4335" d="M12 5.38c1.62 0 3.06.56 4.21 1.64l3.15-3.15C17.45 2.09 14.97 1 12 1a11 11 0 0 0-9.82 6.05l3.66 2.84c.87-2.6 3.3-4.51 6.16-4.51z" />
+          </svg>
+          Sign in with Google
+        </a>
+      </div>
+    )}
+    </>
   )
 
   const renderOtpStep = () => (