* Show 404 error for missing static pages

Updated StaticPageComponent to display an inline 404 error message when a static page is not found, matching the PageNotFoundComponent design. Added translations for the new 404 messages in both English and Czech, and set the server response status to 404 for SSR. Removed legacy error page loading logic and updated tests to mock the new ServerResponseService dependency.

* Improve static page loading and error handling

Refactors static page loading to use a new contentState property ('loading', 'found', 'not-found') for clearer UI state management and error handling. Enhances HtmlContentService with cache-busting and robust fallback logic for localized HTML content. Updates tests and template to reflect new state handling and ensures change detection is triggered after content load or error.

* Use any-cast for changeDetector spies

Replace bracket-indexing (component['changeDetector']) with (component as any).changeDetector in static-page.component.spec.ts. This updates three occurrences in the change-detection tests so TypeScript accepts spying on detectChanges without index-signature errors.

* Make cache-bust deterministic & refactor tests

Use a deterministic cache-bust parameter in HtmlContentService.appendCacheBust (avoid Date.now()) and avoid adding the param if it already exists — this keeps the behavior SSR-safe and cache-friendly. Refactor StaticPageComponent unit tests: allow setupTest to accept undefined HTML, return the mocked responseService, and simplify tests by reusing setupTest to remove duplicated test setup code.

* Add loading indicator and error logging

Show a loading spinner while static page content is fetched and add console.error logging on load failures (includes fileName and URL) to aid debugging. Also simplify HtmlContentService by removing a redundant refetch-on-empty response path that caused an extra network request and special-case 404 handling; a 200 now consistently returns the response body (or empty string). UI behavior for not-found responses remains unchanged.

* Use hourly cache-busting query param

Replace the fixed cache-bust value ('1') with a dynamic hourly value computed from Date.now()/3600000. This appends a changing query parameter so responses are refreshed hourly (reducing stale content) while keeping the existing query-separator logic intact. Removed the prior comment about a deterministic SSR-safe value.

* We don't need to manually duplicate static files

when fallback is working correctly

* Refactor HTML loading, add loading state & tests

Remove cache-busting retry logic from HtmlContentService and simplify loadHtmlContent to a single fetch attempt (returning content on 200, undefined otherwise). Update service unit tests to expect fewer HTTP calls and to not rely on cacheBust query params. Add loading-state handling in StaticPageComponent (reset stale not-found to loading, clear htmlContent at init) and adjust template to avoid rendering the 404 block while async content is pending. Enhance component tests: introduce a createDeferred helper, use fixture.whenStable/detectChanges instead of awaiting ngOnInit directly, and add tests for delayed content resolution and resetting stale not-found state.

* Trigger CI rebuild

* Use fakeAsync and tick in cc-license spec

Wrap the 'getCcLicenseLink' unit test in fakeAsync, add tick(350) and fixture.detectChanges() so the debounced observable has time to emit before the assertion. This ensures the async debounce behavior is handled reliably in the spec.

* fixed failing test

repeat the pattern that the other tests have

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Co-authored-by: Ondrej Kosarko <kosarko@ufal.mff.cuni.cz>
(cherry picked from commit 4a00c7d)