feat(auth): add WorkOS and Keycloak SSO providers (rebased) (#220)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/components/auth/sso-provider-buttons.tsx

@@ -0,0 +1,55 @@
+import React from 'react';
+import type { SsoProviderDiscovery } from '@/lib/sso';
+
+interface SsoProviderButtonsProps {
+  providers: SsoProviderDiscovery[];
+  loadingProviderId?: string | null;
+  onOidcSignIn: (providerId: SsoProviderDiscovery['id']) => void;
+}
+
+export function SsoProviderButtons({
+  providers,
+  loadingProviderId = null,
+  onOidcSignIn,
+}: SsoProviderButtonsProps): React.ReactElement | null {
+  const visibleProviders = providers.filter((provider) => provider.configured);
+
+  if (visibleProviders.length === 0) {
+    return null;
+  }
+
+  return (
+    <div className="mt-6 space-y-3 border-t border-surface-border pt-6">
+      <p className="text-sm font-medium text-text-secondary">Single sign-on</p>
+      <div className="space-y-3">
+        {visibleProviders.map((provider) => {
+          if (provider.loginMode === 'saml' && provider.samlFallback.loginUrl) {
+            return (
+              <a
+                key={provider.id}
+                href={provider.samlFallback.loginUrl}
+                className="flex w-full items-center justify-center rounded-lg border border-surface-border bg-surface-elevated px-4 py-2.5 text-sm font-medium text-text-primary transition-colors hover:border-accent/50 hover:text-accent"
+              >
+                Continue with {provider.name} (SAML)
+              </a>
+            );
+          }
+
+          return (
+            <button
+              key={provider.id}
+              type="button"
+              disabled={loadingProviderId === provider.id}
+              onClick={() => onOidcSignIn(provider.id)}
+              className="flex w-full items-center justify-center rounded-lg border border-surface-border bg-surface-elevated px-4 py-2.5 text-sm font-medium text-text-primary transition-colors hover:border-accent/50 hover:text-accent disabled:opacity-50"
+            >
+              {loadingProviderId === provider.id
+                ? `Redirecting to ${provider.name}...`
+                : `Continue with ${provider.name}`}
+            </button>
+          );
+        })}
+      </div>
+    </div>
+  );
+}