feat: assignee picker in task detail panel

- Quick-assign buttons for Hammer/Donovan/David
- Assignee tracked in save/cancel/dirty detection
- Shows custom assignee names if set by API

frontend/src/components/TaskDetailPanel.tsx

@@ -258,6 +258,7 @@ export function TaskDetailPanel({ task, onClose, onStatusChange, onTaskUpdated,
   const [draftSource, setDraftSource] = useState(task.source);
   const [draftProjectId, setDraftProjectId] = useState(task.projectId || "");
   const [draftDueDate, setDraftDueDate] = useState(task.dueDate ? new Date(task.dueDate).toISOString().slice(0, 16) : "");
+  const [draftAssigneeName, setDraftAssigneeName] = useState(task.assigneeName || "");
   const [projects, setProjects] = useState<Project[]>([]);
   const [newSubtaskTitle, setNewSubtaskTitle] = useState("");
   const [addingSubtask, setAddingSubtask] = useState(false);
@@ -284,7 +285,8 @@ export function TaskDetailPanel({ task, onClose, onStatusChange, onTaskUpdated,
     setDraftSource(task.source);
     setDraftProjectId(task.projectId || "");
     setDraftDueDate(task.dueDate ? new Date(task.dueDate).toISOString().slice(0, 16) : "");
-  }, [task.id, task.title, task.description, task.priority, task.source, task.projectId, task.dueDate]);
+    setDraftAssigneeName(task.assigneeName || "");
+  }, [task.id, task.title, task.description, task.priority, task.source, task.projectId, task.dueDate, task.assigneeName]);
 
   // Detect if any field has been modified
   const currentDueDate = task.dueDate ? new Date(task.dueDate).toISOString().slice(0, 16) : "";
@@ -294,7 +296,8 @@ export function TaskDetailPanel({ task, onClose, onStatusChange, onTaskUpdated,
     draftPriority !== task.priority ||
     draftSource !== task.source ||
     draftProjectId !== (task.projectId || "") ||
-    draftDueDate !== currentDueDate;
+    draftDueDate !== currentDueDate ||
+    draftAssigneeName !== (task.assigneeName || "");
 
   const handleCancel = () => {
     setDraftTitle(task.title);
@@ -303,6 +306,7 @@ export function TaskDetailPanel({ task, onClose, onStatusChange, onTaskUpdated,
     setDraftSource(task.source);
     setDraftProjectId(task.projectId || "");
     setDraftDueDate(task.dueDate ? new Date(task.dueDate).toISOString().slice(0, 16) : "");
+    setDraftAssigneeName(task.assigneeName || "");
   };
 
   const handleSave = async () => {
@@ -316,6 +320,7 @@ export function TaskDetailPanel({ task, onClose, onStatusChange, onTaskUpdated,
       if (draftSource !== task.source) updates.source = draftSource;
       if (draftProjectId !== (task.projectId || "")) updates.projectId = draftProjectId || null;
       if (draftDueDate !== currentDueDate) updates.dueDate = draftDueDate ? new Date(draftDueDate).toISOString() : null;
+      if (draftAssigneeName !== (task.assigneeName || "")) updates.assigneeName = draftAssigneeName || null;
       await updateTask(task.id, updates, token);
       onTaskUpdated();
       toast("Changes saved", "success");
@@ -502,6 +507,45 @@ export function TaskDetailPanel({ task, onClose, onStatusChange, onTaskUpdated,
             </div>
           )}
 
+          {/* Assignee */}
+          <div className="px-4 sm:px-6 py-4 border-b border-gray-100">
+            <h3 className="text-xs font-semibold text-gray-400 uppercase tracking-wider mb-2">Assignee</h3>
+            {hasToken ? (
+              <div className="flex items-center gap-2">
+                <div className="flex gap-1.5 flex-wrap">
+                  {["Hammer", "Donovan", "David"].map((name) => (
+                    <button
+                      key={name}
+                      onClick={() => setDraftAssigneeName(draftAssigneeName === name ? "" : name)}
+                      className={`text-xs px-2.5 py-1.5 rounded-lg font-medium transition border ${
+                        draftAssigneeName === name
+                          ? "bg-emerald-500 text-white border-emerald-500"
+                          : "bg-white text-gray-600 border-gray-200 hover:border-gray-300 hover:bg-gray-50"
+                      }`}
+                    >
+                      👤 {name}
+                    </button>
+                  ))}
+                </div>
+                {draftAssigneeName && !["Hammer", "Donovan", "David"].includes(draftAssigneeName) && (
+                  <span className="text-xs px-2 py-1 bg-emerald-100 text-emerald-700 rounded-full font-medium">
+                    👤 {draftAssigneeName}
+                  </span>
+                )}
+              </div>
+            ) : (
+              <span className="text-sm text-gray-700">
+                {task.assigneeName ? (
+                  <span className="text-xs px-2 py-1 bg-emerald-100 text-emerald-700 rounded-full font-medium">
+                    👤 {task.assigneeName}
+                  </span>
+                ) : (
+                  <span className="text-gray-400 italic">Unassigned</span>
+                )}
+              </span>
+            )}
+          </div>
+
           {/* Due Date */}
           <div className="px-4 sm:px-6 py-4 border-b border-gray-100">
             <h3 className="text-xs font-semibold text-gray-400 uppercase tracking-wider mb-2">Due Date</h3>