feat: notify devices when Following changes (Closes #1313)

tests/e2e/test_mobile_following_release.py

@@ -29,6 +29,12 @@ def test_following_queue_is_phone_usable_at_narrow_viewport(viewport):
         row = page.locator('[data-mobile-queue="following"]')
         expect(row).to_have_count(1)
         expect(row).to_contain_text("Issues and pull requests you watch")
+        following_alert = page.locator('label[for="push-following"]')
+        expect(following_alert).to_have_count(1)
+        expect(following_alert).to_contain_text("Notify me when Following changes")
+        page.locator("#work-settings-toggle").click()
+        expect(following_alert).to_be_visible()
+        assert following_alert.bounding_box()["height"] >= 44
         page.evaluate("""() => {
           globalThis.fetch = async () => ({
             ok:true,