feat(board): edit task deadlines

TaskTracker.Api/Pages/Board.cshtml.cs

@@ -151,7 +151,7 @@ public class BoardModel : PageModel
         return await ReturnBoardContentAsync();
     }
 
-    public async Task<IActionResult> OnPostCreateTaskAsync(string title, string? category)
+    public async Task<IActionResult> OnPostCreateTaskAsync(string title, string? category, DateTime? dueAt)
     {
         if (string.IsNullOrWhiteSpace(title))
             return BadRequest("Title is required.");
@@ -161,6 +161,7 @@ public class BoardModel : PageModel
             Title = title.Trim(),
             Category = category,
             Status = WorkTaskStatus.Pending,
+            DueAt = TaskDeadline.FromLocalInput(dueAt, TimeZoneInfo.Local),
         };
         await _taskRepo.CreateAsync(task);
 
@@ -176,7 +177,7 @@ public class BoardModel : PageModel
     }
 
     // Update task fields (inline edit)
-    public async Task<IActionResult> OnPutUpdateTaskAsync(int id, string? title, string? description, string? category, int? estimatedMinutes)
+    public async Task<IActionResult> OnPutUpdateTaskAsync(int id, string? title, string? description, string? category, int? estimatedMinutes, DateTime? dueAt, bool clearDueAt)
     {
         var task = await _taskRepo.GetByIdAsync(id);
         if (task is null) return NotFound();
@@ -185,6 +186,8 @@ public class BoardModel : PageModel
         if (description is not null) task.Description = description;
         if (category is not null) task.Category = category;
         if (estimatedMinutes.HasValue) task.EstimatedMinutes = estimatedMinutes;
+        if (clearDueAt) task.DueAt = null;
+        else if (dueAt.HasValue) task.DueAt = TaskDeadline.FromLocalInput(dueAt, TimeZoneInfo.Local);
 
         await _taskRepo.UpdateAsync(task);
         return Partial("Partials/_TaskDetail", task);

TaskTracker.Api/Pages/Partials/_CreateTaskForm.cshtml

@@ -8,4 +8,10 @@
            placeholder="New task..."
            class="input"
            autocomplete="off" />
+    <label for="new-task-deadline" class="sr-only">Deadline</label>
+    <input id="new-task-deadline"
+           type="datetime-local"
+           name="dueAt"
+           class="input"
+           aria-label="Deadline" />
 </form>

TaskTracker.Api/Pages/Partials/_TaskDetail.cshtml

@@ -14,6 +14,7 @@
     var (statusColor, statusLabel) = statusColors[Model.Status];
     var catColor = BoardModel.GetCategoryColor(Model.Category);
     var elapsed = BoardModel.FormatElapsed(Model.StartedAt, Model.CompletedAt);
+    var deadlineLocalValue = Model.DueAt?.LocalDateTime.ToString("yyyy-MM-ddTHH:mm");
 
     double? progressPercent = null;
     if (Model.EstimatedMinutes.HasValue && Model.StartedAt.HasValue)
@@ -139,6 +140,31 @@
                     <span style="color: var(--color-text-primary); font-variant-numeric: tabular-nums;">@elapsed</span>
                 </div>
 
+                <div style="display: flex; justify-content: space-between; align-items: center; font-size: 13px;">
+                    <span style="color: var(--color-text-secondary);">Deadline</span>
+                    <div class="inline-edit" id="edit-deadline" style="text-align: right;">
+                        <span class="inline-edit-display inline-edit-display--field"
+                              onclick="startEdit('deadline')"
+                              style="color: var(--color-text-primary); font-variant-numeric: tabular-nums; padding: 2px 8px;">
+                            @(deadlineLocalValue ?? "--")
+                        </span>
+                        <form class="inline-edit-form" style="display:none"
+                              hx-put="/board?handler=UpdateTask&id=@Model.Id"
+                              hx-target="#detail-panel"
+                              hx-swap="innerHTML">
+                            <label for="task-deadline-@Model.Id" class="sr-only">Deadline</label>
+                            <input id="task-deadline-@Model.Id" type="datetime-local" name="dueAt"
+                                   value="@deadlineLocalValue" class="inline-edit-input"
+                                   aria-label="Deadline" />
+                            <div style="display: flex; gap: 6px; margin-top: 6px;">
+                                <button type="submit" class="btn btn--sm btn--primary">Save</button>
+                                <button type="button" class="btn btn--sm btn--ghost" onclick="cancelEdit('deadline')">Cancel</button>
+                                <button type="submit" name="clearDueAt" value="true" class="btn btn--sm btn--ghost">Clear deadline</button>
+                            </div>
+                        </form>
+                    </div>
+                </div>
+
                 <div style="display: flex; justify-content: space-between; align-items: center; font-size: 13px;">
                     <span style="color: var(--color-text-secondary);">Estimate</span>
                     <div class="inline-edit" id="edit-estimate" style="text-align: right;">

TaskTracker.Api/Pages/Shared/TaskDeadline.cs

@@ -0,0 +1,12 @@
+namespace TaskTracker.Api.Pages;
+
+public static class TaskDeadline
+{
+    public static DateTimeOffset? FromLocalInput(DateTime? localValue, TimeZoneInfo timeZone)
+    {
+        if (!localValue.HasValue) return null;
+
+        var unspecified = DateTime.SpecifyKind(localValue.Value, DateTimeKind.Unspecified);
+        return new DateTimeOffset(unspecified, timeZone.GetUtcOffset(unspecified));
+    }
+}