feat(shared-ui,shared-stores): add FavoriteButton component and toggleField utility

FavoriteButton: reusable heart/star/pin toggle with filled/outline states,
accessible labels, configurable colors. toggleField: generic boolean field
toggle for Dexie records (isFavorite, isPinned, etc.) with timestamp.
Includes 11 tests (6 FavoriteButton + 5 toggleField).

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

packages/shared-stores/src/index.ts

@@ -45,3 +45,10 @@ export {
 	type LocalTagGroup,
 } from './tags-local.svelte';
 export { createTagLinkOps, type TagLinkOps, type TagLinkOpsConfig } from './tag-links';
+export { toggleField } from './toggle-field';
+export {
+	createGuestMode,
+	type GuestMode,
+	type GuestModeOptions,
+	type GuestModeNotification,
+} from './guest-mode.svelte';

packages/shared-stores/src/toggle-field.test.ts

@@ -0,0 +1,49 @@
+import { describe, it, expect, vi } from 'vitest';
+import { toggleField } from './toggle-field';
+
+function createMockTable(records: Record<string, Record<string, unknown>>) {
+	return {
+		get: vi.fn(async (id: string) => records[id] ?? null),
+		update: vi.fn(async (id: string, changes: Record<string, unknown>) => {
+			if (records[id]) Object.assign(records[id], changes);
+			return 1;
+		}),
+	};
+}
+
+describe('toggleField', () => {
+	it('toggles false to true', async () => {
+		const table = createMockTable({ '1': { id: '1', isFavorite: false } });
+		const result = await toggleField(table as never, '1', 'isFavorite');
+		expect(result).toBe(true);
+		expect(table.update).toHaveBeenCalledWith('1', expect.objectContaining({ isFavorite: true }));
+	});
+
+	it('toggles true to false', async () => {
+		const table = createMockTable({ '1': { id: '1', isFavorite: true } });
+		const result = await toggleField(table as never, '1', 'isFavorite');
+		expect(result).toBe(false);
+		expect(table.update).toHaveBeenCalledWith('1', expect.objectContaining({ isFavorite: false }));
+	});
+
+	it('sets updatedAt timestamp', async () => {
+		const table = createMockTable({ '1': { id: '1', isPinned: false } });
+		await toggleField(table as never, '1', 'isPinned');
+		const call = table.update.mock.calls[0][1] as Record<string, unknown>;
+		expect(call.updatedAt).toBeTruthy();
+		expect(typeof call.updatedAt).toBe('string');
+	});
+
+	it('throws if record not found', async () => {
+		const table = createMockTable({});
+		await expect(toggleField(table as never, 'missing', 'isFavorite')).rejects.toThrow(
+			'Record missing not found'
+		);
+	});
+
+	it('treats undefined as false', async () => {
+		const table = createMockTable({ '1': { id: '1' } });
+		const result = await toggleField(table as never, '1', 'isFavorite');
+		expect(result).toBe(true);
+	});
+});

packages/shared-stores/src/toggle-field.ts

@@ -0,0 +1,42 @@
+/**
+ * Generic boolean field toggle for Dexie tables.
+ *
+ * Standardizes the common pattern of toggling a boolean field (isFavorite, isPinned, etc.)
+ * on a record in IndexedDB. Reads current value, flips it, updates with timestamp.
+ *
+ * @example
+ * ```typescript
+ * import { toggleField } from '@manacore/shared-stores';
+ * import { db } from '$lib/data/database';
+ *
+ * // In your store:
+ * async function toggleFavorite(id: string) {
+ *   return toggleField(db.table('contacts'), id, 'isFavorite');
+ * }
+ * ```
+ */
+
+import type { Table } from 'dexie';
+
+/**
+ * Toggle a boolean field on a Dexie record.
+ * @returns The new value of the field after toggling.
+ */
+export async function toggleField<T>(
+	table: Table<T, string>,
+	id: string,
+	field: string
+): Promise<boolean> {
+	const record = await table.get(id);
+	if (!record) throw new Error(`Record ${id} not found`);
+
+	const current = !!(record as Record<string, unknown>)[field];
+	const newValue = !current;
+
+	await table.update(id, {
+		[field]: newValue,
+		updatedAt: new Date().toISOString(),
+	} as Partial<T>);
+
+	return newValue;
+}