feat(#415): theme fix, AuthDivider, SessionExpiryWarning components

- AUTH-014: Fix theme storage key (jarvis-theme -> mosaic-theme)
- AUTH-016: Create AuthDivider component with customizable text
- AUTH-019: Create SessionExpiryWarning floating banner (PDA-friendly, blue)
- Fix lint errors in LoginForm, OAuthButton from parallel agents
- Sync pnpm-lock.yaml for recharts dependency

Refs #415

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/components/auth/AuthErrorBanner.tsx

@@ -0,0 +1,32 @@
+"use client";
+
+import type { ReactElement } from "react";
+import { Info, X } from "lucide-react";
+
+export interface AuthErrorBannerProps {
+  message: string;
+  onDismiss?: () => void;
+}
+
+export function AuthErrorBanner({ message, onDismiss }: AuthErrorBannerProps): ReactElement {
+  return (
+    <div
+      role="alert"
+      aria-live="polite"
+      className="bg-blue-50 border border-blue-200 text-blue-700 rounded-lg p-4 flex items-start gap-3"
+    >
+      <Info className="h-5 w-5 flex-shrink-0 mt-0.5" aria-hidden="true" />
+      <span className="flex-1 text-sm">{message}</span>
+      {onDismiss && (
+        <button
+          type="button"
+          onClick={onDismiss}
+          className="flex-shrink-0 text-blue-500 hover:text-blue-700 transition-colors"
+          aria-label="Dismiss"
+        >
+          <X className="h-4 w-4" aria-hidden="true" />
+        </button>
+      )}
+    </div>
+  );
+}