fix: Timesheet naming and todo auto-assign fixes

- Fix timesheet filename to use firstName-lastName format with username fallback
- Remove auto-assign creator to todos (user must manually select assignees)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/services/todo.service.js

@@ -209,16 +209,6 @@ export const createTodo = async (userId, data) => {
     await db.insert(todoUsers).values(todoUserInserts);
   }
 
-  // Auto-assign the creator to the todo so they can access it (if not already assigned)
-  const creatorAlreadyAssigned = assignedUserIds && assignedUserIds.includes(userId);
-  if (!creatorAlreadyAssigned) {
-    await db.insert(todoUsers).values({
-      todoId: newTodo.id,
-      userId: userId,
-      assignedBy: userId,
-    });
-  }
-
   // Send push notifications to assigned users (excluding creator)
   if (assignedUserIds && Array.isArray(assignedUserIds) && assignedUserIds.length > 0) {
     try {