feat(web): add "New Task" button scroll-to-input behavior

Clicking the header "New Task" button now scrolls to and focuses
the create-task input in the Pending column.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

TaskTracker.Api/wwwroot/js/app.js

@@ -111,6 +111,18 @@
     // Initialize Kanban drag-and-drop on page load
     document.addEventListener('DOMContentLoaded', function() {
         initKanban();
+
+        // "New Task" header button — scroll to and focus the create-task input in the Pending column
+        var newTaskBtn = document.getElementById('new-task-trigger');
+        if (newTaskBtn) {
+            newTaskBtn.addEventListener('click', function() {
+                var input = document.querySelector('.create-task-form input[name="title"]');
+                if (input) {
+                    input.scrollIntoView({ behavior: 'smooth', block: 'center' });
+                    input.focus();
+                }
+            });
+        }
     });
 
     // Re-initialize after htmx swaps that affect the kanban board.