feat: unified guest mode with AuthGate + createGuestMode composable

Major refactor of ManaCore's (app) layout for guest mode support:

- New createGuestMode() composable in shared-stores — encapsulates
  welcome modal state, nudge timer, and notifications in one call
- Replace monolith onMount with AuthGate + handleAuthReady callback:
  Phase A (auth-independent): DB init, migration, uload, dashboard
  Phase B (auth-dependent): sync, user settings, onboarding
  Phase C (guest-only): welcome modal + registration nudge
- Root route / always redirects to /home (no auth check)
- PillNav shows login button for guests, user email for auth users
- GuestWelcomeModal with manacore-specific features
- SessionWarning only renders for authenticated users
- Proper cleanup via onDestroy

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

packages/shared-stores/src/guest-mode.svelte.ts

@@ -0,0 +1,130 @@
+/**
+ * Guest Mode Composable
+ *
+ * Encapsulates welcome modal visibility, registration nudge timer,
+ * and bottom notification state for guest users.
+ *
+ * Usage:
+ *   const guestMode = createGuestMode('manacore', { nudgeDelayMinutes: 3 });
+ */
+
+// Inline localStorage utilities (no external dependency needed)
+function _shouldShowWelcome(appId: string): boolean {
+	if (typeof localStorage === 'undefined') return false;
+	return localStorage.getItem(`guest-welcome-seen-${appId}`) !== 'true';
+}
+
+function _markWelcomeSeen(appId: string): void {
+	if (typeof localStorage === 'undefined') return;
+	localStorage.setItem(`guest-welcome-seen-${appId}`, 'true');
+}
+
+function _startSession(appId: string): void {
+	if (typeof localStorage === 'undefined') return;
+	const key = `guest-nudge-session-${appId}`;
+	if (!localStorage.getItem(key)) {
+		localStorage.setItem(key, Date.now().toString());
+	}
+}
+
+function _shouldShowNudge(appId: string, delayMinutes: number): boolean {
+	if (typeof localStorage === 'undefined') return false;
+	if (localStorage.getItem(`guest-nudge-dismissed-${appId}`) === 'true') return false;
+	const sessionStart = localStorage.getItem(`guest-nudge-session-${appId}`);
+	if (!sessionStart) return false;
+	return Date.now() - parseInt(sessionStart, 10) >= delayMinutes * 60 * 1000;
+}
+
+function _dismissNudge(appId: string): void {
+	if (typeof localStorage === 'undefined') return;
+	localStorage.setItem(`guest-nudge-dismissed-${appId}`, 'true');
+}
+
+export interface GuestModeNotification {
+	id: string;
+	message: string;
+	type: 'info' | 'warning' | 'error';
+	action?: { label: string; icon?: unknown; onClick: () => void };
+	dismissible?: boolean;
+	onDismiss?: () => void;
+}
+
+export interface GuestModeOptions {
+	nudgeDelayMinutes?: number;
+	nudgeCheckIntervalMs?: number;
+	nudgeMessage?: string;
+	nudgeActionLabel?: string;
+	onRegister?: () => void;
+}
+
+export interface GuestMode {
+	readonly showWelcome: boolean;
+	readonly notifications: GuestModeNotification[];
+	dismissWelcome(): void;
+	destroy(): void;
+}
+
+export function createGuestMode(appId: string, opts?: GuestModeOptions): GuestMode {
+	const nudgeDelay = opts?.nudgeDelayMinutes ?? 5;
+	const checkInterval = opts?.nudgeCheckIntervalMs ?? 30_000;
+	const nudgeMessage =
+		opts?.nudgeMessage ?? 'Gefällt es dir? Sichere deine Daten geräteübergreifend.';
+	const nudgeActionLabel = opts?.nudgeActionLabel ?? 'Konto erstellen';
+
+	let showWelcome = $state(_shouldShowWelcome(appId));
+	let notifications = $state<GuestModeNotification[]>([]);
+	let nudgeInterval: ReturnType<typeof setInterval> | null = null;
+
+	_startSession(appId);
+
+	function checkNudge() {
+		if (_shouldShowNudge(appId, nudgeDelay)) {
+			notifications = [
+				{
+					id: 'guest-nudge',
+					message: nudgeMessage,
+					type: 'info' as const,
+					action: {
+						label: nudgeActionLabel,
+						onClick: () => {
+							_dismissNudge(appId);
+							notifications = [];
+							opts?.onRegister?.();
+						},
+					},
+					dismissible: true,
+					onDismiss: () => {
+						_dismissNudge(appId);
+						notifications = [];
+					},
+				},
+			];
+			if (nudgeInterval) {
+				clearInterval(nudgeInterval);
+				nudgeInterval = null;
+			}
+		}
+	}
+
+	checkNudge();
+	nudgeInterval = setInterval(checkNudge, checkInterval);
+
+	return {
+		get showWelcome() {
+			return showWelcome;
+		},
+		get notifications() {
+			return notifications;
+		},
+		dismissWelcome() {
+			showWelcome = false;
+			_markWelcomeSeen(appId);
+		},
+		destroy() {
+			if (nudgeInterval) {
+				clearInterval(nudgeInterval);
+				nudgeInterval = null;
+			}
+		},
+	};
+}

packages/shared-stores/src/index.ts

@@ -46,6 +46,7 @@ export {
 } from './tags-local.svelte';
 export { createTagLinkOps, type TagLinkOps, type TagLinkOpsConfig } from './tag-links';
 export { toggleField } from './toggle-field';
+
 export {
 	createGuestMode,
 	type GuestMode,