feat: add drag-and-drop task reordering (#14, #15, #16)

public/app.js

@@ -270,7 +270,8 @@ function renderBoard() {
           headers: { 'Content-Type': 'application/json' },
           body: JSON.stringify({ status: 'Done' }),
         });
-        loadTasks();
+        initDragAndDrop();
+  loadTasks();
       });
 
       cardsEl.appendChild(cardEl);
@@ -328,11 +329,13 @@ function initTasksPage() {
     });
 
     e.target.reset();
-    loadTasks();
+    initDragAndDrop();
+  loadTasks();
   });
 
   initTaskFilters();
   populateAgentDropdown();
+  initDragAndDrop();
   loadTasks();
 }
 
@@ -1375,3 +1378,69 @@ function renderGiteaActivity() {
     </div>
   `).join('');
 }
+
+// ============ DRAG AND DROP ============
+let draggedTask = null;
+
+function initDragAndDrop() {
+  const board = document.getElementById('board');
+  if (!board) return;
+  
+  // Add drag listeners to columns
+  document.querySelectorAll('.column').forEach(column => {
+    column.addEventListener('dragover', handleDragOver);
+    column.addEventListener('drop', handleDrop);
+    column.addEventListener('dragleave', handleDragLeave);
+  });
+}
+
+function handleDragOver(e) {
+  e.preventDefault();
+  e.currentTarget.classList.add('drag-over');
+}
+
+function handleDragLeave(e) {
+  e.currentTarget.classList.remove('drag-over');
+}
+
+async function handleDrop(e) {
+  e.preventDefault();
+  const column = e.currentTarget;
+  column.classList.remove('drag-over');
+  
+  if (!draggedTask) return;
+  
+  const newStatus = column.dataset.status;
+  if (newStatus === draggedTask.status) return;
+  
+  // Update task status via API
+  try {
+    await fetch(`/api/tasks/${draggedTask.id}`, {
+      method: 'PATCH',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ status: newStatus })
+    });
+    
+    // Reload tasks
+    await initDragAndDrop();
+  loadTasks();
+  } catch (err) {
+    console.error('Failed to update task:', err);
+  }
+  
+  draggedTask = null;
+}
+
+function makeTaskCardDraggable(cardEl, task) {
+  cardEl.draggable = true;
+  
+  cardEl.addEventListener('dragstart', (e) => {
+    draggedTask = task;
+    cardEl.classList.add('dragging');
+    e.dataTransfer.effectAllowed = 'move';
+  });
+  
+  cardEl.addEventListener('dragend', () => {
+    cardEl.classList.remove('dragging');
+  });
+}