feat: Integrate sync status indicators in app title bar and home screen

lib/widgets/search_app_bar.dart

@@ -7,6 +7,8 @@ class SearchAppBar extends StatefulWidget {
     this.onLeadingPressed,
     this.leadingIcon = Icons.menu,
     this.leadingTooltip = 'Menú',
+    this.leadingWidget,
+    this.trailingWidget,
     this.onSearchChanged,
     this.searchHint = 'Buscar notas...',
     this.showSearch = true,
@@ -17,6 +19,8 @@ class SearchAppBar extends StatefulWidget {
   final VoidCallback? onLeadingPressed;
   final IconData leadingIcon;
   final String leadingTooltip;
+  final Widget? leadingWidget;
+  final Widget? trailingWidget;
   final ValueChanged<String>? onSearchChanged;
   final String searchHint;
   final bool showSearch;
@@ -67,6 +71,10 @@ class _SearchAppBarState extends State<SearchAppBar> {
             splashRadius: 18,
             constraints: const BoxConstraints(minWidth: 40, minHeight: 40),
           ),
+          if (widget.leadingWidget != null) ...[
+            const SizedBox(width: 8),
+            Center(child: widget.leadingWidget!),
+          ],
           const SizedBox(width: 8),
           Expanded(
             child: widget.showSearch
@@ -151,6 +159,10 @@ class _SearchAppBarState extends State<SearchAppBar> {
                     ),
                   ),
           ),
+          if (widget.trailingWidget != null) ...[
+            const SizedBox(width: 8),
+            Center(child: widget.trailingWidget!),
+          ],
         ],
       ),
     );