feat(shared-auth-ui): add GuestRegistrationNudge + complete feature texts + improve seed data

- Add GuestRegistrationNudge component: shows a floating banner after
  X minutes of guest usage to encourage sign-up (bottom-center, dismissible)
- Add guestNudge.ts utilities (session tracking, delay, dismiss via localStorage)
- Add feature texts for all 16 missing apps in GuestWelcomeModal
- Integrate nudge in Todo app as reference implementation (3min delay)
- Improve SkillTree seed: 3 skills across branches, 6 activities, 1 achievement
- Improve Zitare seed: 5 favorites, 2 themed lists instead of 1

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/shared-auth-ui/src/utils/guestNudge.ts

@@ -0,0 +1,69 @@
+/**
+ * Utility functions for managing guest registration nudge state.
+ * Shows a nudge after X minutes of guest usage to encourage sign-up.
+ */
+
+const SESSION_PREFIX = 'guest-nudge-session';
+const DISMISSED_PREFIX = 'guest-nudge-dismissed';
+
+/**
+ * Record the start of a guest session for an app (call once on mount).
+ * Only sets the timestamp if one doesn't already exist.
+ */
+export function startGuestSession(appId: string): void {
+	if (typeof localStorage === 'undefined') return;
+	const key = `${SESSION_PREFIX}-${appId}`;
+	if (!localStorage.getItem(key)) {
+		localStorage.setItem(key, Date.now().toString());
+	}
+}
+
+/**
+ * Check if enough time has passed to show the registration nudge.
+ * Returns false if already dismissed or not enough time elapsed.
+ */
+export function shouldShowGuestNudge(appId: string, delayMinutes = 5): boolean {
+	if (typeof localStorage === 'undefined') return false;
+
+	// Already dismissed?
+	if (localStorage.getItem(`${DISMISSED_PREFIX}-${appId}`) === 'true') return false;
+
+	// Check elapsed time
+	const sessionStart = localStorage.getItem(`${SESSION_PREFIX}-${appId}`);
+	if (!sessionStart) return false;
+
+	const elapsed = Date.now() - parseInt(sessionStart, 10);
+	return elapsed >= delayMinutes * 60 * 1000;
+}
+
+/**
+ * Permanently dismiss the nudge for an app.
+ */
+export function dismissGuestNudge(appId: string): void {
+	if (typeof localStorage === 'undefined') return;
+	localStorage.setItem(`${DISMISSED_PREFIX}-${appId}`, 'true');
+}
+
+/**
+ * Reset nudge state for an app (will show again after delay).
+ */
+export function resetGuestNudge(appId: string): void {
+	if (typeof localStorage === 'undefined') return;
+	localStorage.removeItem(`${SESSION_PREFIX}-${appId}`);
+	localStorage.removeItem(`${DISMISSED_PREFIX}-${appId}`);
+}
+
+/**
+ * Reset nudge state for all apps.
+ */
+export function resetAllGuestNudges(): void {
+	if (typeof localStorage === 'undefined') return;
+	const keysToRemove: string[] = [];
+	for (let i = 0; i < localStorage.length; i++) {
+		const key = localStorage.key(i);
+		if (key?.startsWith(SESSION_PREFIX) || key?.startsWith(DISMISSED_PREFIX)) {
+			keysToRemove.push(key);
+		}
+	}
+	keysToRemove.forEach((key) => localStorage.removeItem(key));
+}