Fix browse filters having no effect due to filter-agnostic cache key

The MinIO cache key only encoded page number, so all filter combinations
hit the same cache entry and returned unfiltered results. Introduce
BrowseFilteredHTMLKey() that encodes sort/genre/status into the key
(e.g. novelfire.net/html/new-isekai-completed/page-1.html); falls back
to the original page-only key for default filters to preserve existing
cached pages.

scraper/internal/orchestrator/orchestrator_test.go

@@ -155,8 +155,9 @@ func (s *mockStore) SaveBrowsePage(_ context.Context, _, _ string) error { retur
 func (s *mockStore) GetBrowsePage(_ context.Context, _ string) (string, bool, error) {
 	return "", false, nil
 }
-func (s *mockStore) BrowseHTMLKey(_ string, _ int) string { return "" }
-func (s *mockStore) BrowseCoverKey(_, _ string) string    { return "" }
+func (s *mockStore) BrowseHTMLKey(_ string, _ int) string                         { return "" }
+func (s *mockStore) BrowseFilteredHTMLKey(_ string, _ int, _, _, _ string) string { return "" }
+func (s *mockStore) BrowseCoverKey(_, _ string) string                            { return "" }
 func (s *mockStore) SaveBrowseAsset(_ context.Context, _ string, _ []byte, _ string) error {
 	return nil
 }