refactor: complete zoneless Angular migration

[sawankshrma]

• The application now uses provideZonelessChangeDetection() instead of provideZoneChangeDetection().
• Removed zone.js from the application dependencies and from the build/test polyfills, including the zone.js/testing test bootstrap import.
• Replaced the remaining Zone-dependent fakeAsync / tick test setup with native async / await fixture.whenStable().
• Migrated the remaining loading and rendered-content state in ActivityDescriptionPageComponent, ReportComponent, UsageComponent, and MarkdownViewerComponent to signals so their templates update correctly without Zone.js.
• DSOMM is now completely zoneless at runtime and in its test configuration 🎉.
• Files: angular.json, package.json, package-lock.json, src/main.ts, src/test.ts, src/app/pages/settings/settings.component.spec.ts, src/app/component/markdown-viewer/*, src/app/pages/activity-description/*, src/app/pages/report/*, src/app/pages/usage/*

[sawankshrma]

Note for Reviewers:

I've thoroughly tested all UI functionality in the app, but since this PR changes the underlying UI rendering process end-to-end, some non-trivial or less obvious functionality may have been missed.

• I'd recommend doing an independent pass over the app's UI as well to catch anything that might not be immediately apparent.