fix: Further improvements on app theming

lib/ui/widgets/shared/custom_popup_menu.dart

@@ -15,6 +15,10 @@ class CustomPopupMenu extends StatelessWidget {
     return Theme(
       data: Theme.of(context).copyWith(useMaterial3: false),
       child: PopupMenuButton<int>(
+        icon: Icon(
+          Icons.more_vert,
+          color: Theme.of(context).colorScheme.secondary,
+        ),
         onSelected: onSelected,
         itemBuilder: (context) => children.entries
             .map(

lib/ui/widgets/shared/custom_sliver_app_bar.dart

@@ -26,10 +26,7 @@ class CustomSliverAppBar extends StatelessWidget {
             : Theme.of(context).canvasColor,
       ),
       flexibleSpace: FlexibleSpaceBar(
-        titlePadding: const EdgeInsets.symmetric(
-          vertical: 23.0,
-          horizontal: 20.0,
-        ),
+        titlePadding: const EdgeInsets.only(bottom: 16.0, left: 20.0),
         title: title,
       ),
       actions: actions,

lib/ui/widgets/shared/search_bar.dart

@@ -36,6 +36,9 @@ class _SearchBarState extends State<SearchBar> {
             child: TextFormField(
               onChanged: widget.onQueryChanged,
               controller: _textController,
+              style: TextStyle(
+                color: Theme.of(context).colorScheme.secondary,
+              ),
               decoration: InputDecoration(
                 filled: true,
                 fillColor: Theme.of(context).colorScheme.secondaryContainer,