You do not need a special travel app. An ordinary chatbot is enough for this short text task. Free options such as Gemini and ChatGPT work, although they have different usage limits. Do not give the AI more personal information than it needs.
The result can be more useful than packing ten tops at random. A rain jacket, comfortable shoes, a layer for cool evenings and a charger come first. Dinner clothes and work items get their own lines.
Check the weather, medication, tickets and baggage rules yourself. AI is good at organising your thoughts, but it does not know if your particular trip changes tomorrow.