fix(usage): keep records refreshing in background

- refresh usage records when the WebView is hidden or occluded
- disable WebView2 background throttling for the main window
- add regression coverage for background refresh behavior

tests/usageBackgroundRefresh.test.ts

@@ -0,0 +1,32 @@
+import { describe, expect, it } from 'bun:test';
+import { readFileSync } from 'node:fs';
+
+describe('usage records background refresh', () => {
+  it('keeps refresh triggers active when the document is hidden', () => {
+    const source = readFileSync(
+      new URL('../src/pages/UsageRecordsPage.tsx', import.meta.url),
+      'utf8',
+    );
+    const refreshStart = source.indexOf('const refresh = () => {');
+    const refreshEnd = source.indexOf("listen('usage-records-updated'", refreshStart);
+    const refreshBlock = source.slice(refreshStart, refreshEnd);
+
+    expect(refreshStart).toBeGreaterThanOrEqual(0);
+    expect(refreshEnd).toBeGreaterThan(refreshStart);
+    expect(refreshBlock).toContain('if (!disposed) void loadData(true, true);');
+    expect(refreshBlock).not.toContain('document.hidden');
+  });
+
+  it('disables WebView background suspension for the desktop window', () => {
+    const config = JSON.parse(
+      readFileSync(new URL('../src-tauri/tauri.conf.json', import.meta.url), 'utf8'),
+    );
+    const mainWindow = config.app.windows.find((window: { label?: string }) => window.label === 'main');
+    const browserArgs = String(mainWindow?.additionalBrowserArgs ?? '').split(/\s+/);
+
+    expect(mainWindow?.backgroundThrottling).toBe('disabled');
+    expect(browserArgs).toContain('--disable-background-timer-throttling');
+    expect(browserArgs).toContain('--disable-renderer-backgrounding');
+    expect(browserArgs).toContain('--disable-backgrounding-occluded-windows');
+  });
+});