Phase 10: command palette, settings, backup/restore, sample campaign

- Command palette (Ctrl/Cmd+K): fuzzy search over pages + active-campaign
  characters/notes/NPCs/quests + actions; keyboard nav; header ⌘K button
- Settings page: theme, full backup export/import (restore replaces all in one
  transaction), load sample campaign, danger-zone clear-all
- Backup lib (src/lib/io/backup.ts) snapshots every table; sample seeder
  (src/lib/sample.ts) builds a demo campaign
- Header gets ⌘K + settings gear; routes + nav wired

Backup round-trip unit tests + command-palette/settings e2e.
(Deferred from this phase, noted in plan: audio, Discord/Foundry/Roll20, i18n,
push notifications.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

e2e/settings.spec.ts

@@ -0,0 +1,29 @@
+import { test, expect } from '@playwright/test';
+
+test.beforeEach(async ({ page }) => {
+  await page.goto('/');
+  await page.evaluate(async () => {
+    indexedDB.deleteDatabase('ttrpg-manager');
+    localStorage.clear();
+  });
+  await page.reload();
+});
+
+test('command palette navigates', async ({ page }) => {
+  await page.keyboard.press('Control+k');
+  const input = page.getByLabel('Command search');
+  await expect(input).toBeVisible();
+  await input.fill('Dice');
+  await input.press('Enter');
+  await expect(page.getByRole('heading', { name: 'Dice' })).toBeVisible();
+});
+
+test('settings loads the sample campaign', async ({ page }) => {
+  await page.getByLabel('Settings').click();
+  await expect(page.getByRole('heading', { name: 'Settings' })).toBeVisible();
+  await page.getByRole('button', { name: 'Load sample campaign' }).click();
+  await expect(page.getByRole('heading', { name: 'Sample: Lost Mine' })).toBeVisible();
+  // sample seeded characters (use the nav link, not the dashboard card)
+  await page.getByLabel('Primary').getByRole('link', { name: 'Characters' }).click();
+  await expect(page.getByText('Lia the Brave')).toBeVisible();
+});