feat(board): add live task countdowns

TaskTracker.Api/Pages/Partials/_UpcomingTasks.cshtml

@@ -16,7 +16,7 @@
                 var dueAt = task.DueAt!.Value;
                 var dueAtUtc = dueAt.ToUniversalTime().ToString("O");
                 var localDueAt = dueAt.ToLocalTime().ToString("ddd, MMM d, h:mm tt");
-                <article class="upcoming-task"
+                <article class="upcoming-task" data-due-at="@dueAtUtc"
                          hx-get="/board?handler=TaskDetail&id=@task.Id"
                          hx-target="#detail-panel"
                          hx-swap="innerHTML">
@@ -29,7 +29,7 @@
                             <span>@task.Category</span>
                         }
                     </div>
-                    <time class="task-countdown" aria-live="off" data-due-at="@dueAtUtc" datetime="@dueAtUtc" title="@localDueAt">@localDueAt</time>
+                    <time class="task-countdown" aria-live="off" datetime="@dueAtUtc" title="@localDueAt">@localDueAt</time>
                 </article>
             }
         </div>

TaskTracker.Api/wwwroot/js/app.js

@@ -55,6 +55,50 @@
         });
     }
 
+    // ========================================
+    // Upcoming task countdowns
+    // ========================================
+
+    var countdownTimer = null;
+
+    function formatCountdown(totalSeconds, isFuture) {
+        var remaining = totalSeconds;
+        var days = Math.floor(remaining / 86400);
+        remaining %= 86400;
+        var hours = Math.floor(remaining / 3600);
+        remaining %= 3600;
+        var minutes = Math.floor(remaining / 60);
+        var seconds = remaining % 60;
+        var parts = [];
+
+        if (days) parts.push(days + 'd');
+        if (hours) parts.push(hours + 'h');
+        if (minutes) parts.push(minutes + 'm');
+        if (seconds && !days && !hours) parts.push(seconds + 's');
+        if (parts.length === 0) parts.push('0s');
+
+        return isFuture ? parts.join(' ') + ' remaining' : 'Overdue by ' + parts.join(' ');
+    }
+
+    function updateCountdowns() {
+        var now = Date.now();
+        document.querySelectorAll('[data-due-at] .task-countdown, time.task-countdown[data-due-at]').forEach(function(countdown) {
+            var dueAtElement = countdown.closest('[data-due-at]') || countdown;
+            var dueAt = Date.parse(dueAtElement.dataset.dueAt);
+            if (Number.isNaN(dueAt)) return;
+
+            var deltaMilliseconds = dueAt - now;
+            var totalSeconds = Math.floor(Math.abs(deltaMilliseconds) / 1000);
+            countdown.textContent = formatCountdown(totalSeconds, deltaMilliseconds > 0);
+        });
+    }
+
+    function initCountdowns() {
+        if (countdownTimer) clearInterval(countdownTimer);
+        updateCountdowns();
+        countdownTimer = setInterval(updateCountdowns, 1000);
+    }
+
     // ========================================
     // Detail Panel helpers
     // ========================================
@@ -111,6 +155,7 @@
     // Initialize Kanban drag-and-drop on page load
     document.addEventListener('DOMContentLoaded', function() {
         initKanban();
+        initCountdowns();
 
         // "New Task" header button — scroll to and focus the create-task input in the Pending column
         var newTaskBtn = document.getElementById('new-task-trigger');
@@ -132,6 +177,11 @@
         if (target && (target.id === 'kanban-board' || target.id === 'board-content' || (target.closest && target.closest('#kanban-board')))) {
             initKanban();
         }
+        if (target && (target.id === 'board-content' ||
+            (target.matches && target.matches('.upcoming-tasks')) ||
+            (target.querySelector && target.querySelector('.upcoming-tasks')))) {
+            initCountdowns();
+        }
     });
 
     // Also handle htmx:afterSettle for cases where the DOM isn't fully ready on afterSwap