fix(ui): make mobile task creation button compact

ui/flutter/lib/features/tasks/presentation/widgets/task_create_button.dart

@@ -1,3 +1,4 @@
+import 'package:shadcn_flutter/shadcn_flutter.dart' as shad;
 import 'package:flutter/material.dart' show Icons;
 import 'package:flutter/widgets.dart';
 
@@ -7,10 +8,11 @@ import '../../../../shared/widgets/app_primary_button.dart';
 
 /// Shared creation action for task headers and empty-list guidance.
 class TaskCreateButton extends StatelessWidget {
-  const TaskCreateButton({super.key, required this.onPressed, this.minHeight = 0});
+  const TaskCreateButton({super.key, required this.onPressed, this.minHeight = 0, this.compact = false});
 
   final VoidCallback onPressed;
   final double minHeight;
+  final bool compact;
 
   @override
   Widget build(BuildContext context) {
@@ -18,12 +20,20 @@ class TaskCreateButton extends StatelessWidget {
       constraints: BoxConstraints(minHeight: minHeight),
       child: AppPrimaryButton(
         onPressed: onPressed,
+        size: compact ? shad.ButtonSize.small : shad.ButtonSize.normal,
         child: Row(
           mainAxisSize: MainAxisSize.min,
           children: [
-            const Icon(Icons.add),
-            const SizedBox(width: AppDesignTokens.space8),
-            Flexible(child: Text(context.l10n.create, maxLines: 1, overflow: TextOverflow.ellipsis)),
+            Icon(Icons.add, size: compact ? 16 : null),
+            SizedBox(width: compact ? AppDesignTokens.space4 : AppDesignTokens.space8),
+            Flexible(
+              child: Text(
+                context.l10n.create,
+                maxLines: 1,
+                overflow: TextOverflow.ellipsis,
+                style: compact ? const TextStyle(fontSize: 13) : null,
+              ),
+            ),
           ],
         ),
       ),