refactor: navigation/offline handling

and other improvments

lib/mixins/refreshable.dart

@@ -1,3 +1,23 @@
 mixin Refreshable {
   void refresh();
 }
+
+/// Mixin for screens that support full refresh (clearing all cached data)
+mixin FullRefreshable {
+  void fullRefresh();
+}
+
+/// Mixin for screens with focusable tab content
+mixin FocusableTab {
+  void focusActiveTabIfReady();
+}
+
+/// Mixin for screens with focusable search input
+mixin SearchInputFocusable {
+  void focusSearchInput();
+}
+
+/// Mixin for screens that can load a specific library by key
+mixin LibraryLoadable {
+  void loadLibraryByKey(String libraryGlobalKey);
+}