Prepare v2.0.74 sidepanel reliability release

Restore and persist the package-based link collector with progressive metadata, bounded high-volume updates, safe hydration, visible selection, and complete localization.

Harden download controls, snapshot ordering, history pagination, statistics recovery, settings saves, backup imports, notification persistence, and Windows storage races with regression coverage.

tests/backup-payload.test.ts

@@ -19,6 +19,19 @@ const statistics: StatisticsLedger = { version: 2, startedAt: 1, days: [], minut
 const baseInput = { appVersion: "1.7.183", exportedAt: "2026-06-07T00:00:00Z", session, history, statistics };
 
 describe("buildBackupPayload — default is settings-only", () => {
+  it("keeps the semantic theme preference in exported settings", () => {
+    const payload = buildBackupPayload({
+      ...baseInput,
+      settings: settings({ theme: "dark", themePreference: "system" })
+    });
+
+    expect(payload.settings).toEqual(expect.objectContaining({
+      theme: "dark",
+      themePreference: "system"
+    }));
+    expect((JSON.parse(JSON.stringify(payload)) as { settings: AppSettings }).settings.themePreference).toBe("system");
+  });
+
   it("keeps the Deepbrid key only inside the encrypted backup payload", () => {
     const key = "fixture-deepbrid-backup-key-4eF6";
     const payload = buildBackupPayload({