Add Streamlit AI travel agent app

.env.example

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+# Copy this file to .env and set your OpenAI credentials
+OPENAI_API_KEY=sk-your-key-here

.gitignore

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+__pycache__/
+.env
+.streamlit/
+*.pyc

README.md

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-# hello-world
-first project
+# 🧭 AI Travel Agent
+
+A Streamlit application that crafts personalized travel itineraries using OpenAI's generative models. The project is inspired by [ashumishra2104/AI_Travel_agent_Streamlit](https://github.com/ashumishra2104/AI_Travel_agent_Streamlit) and reimagined with a modern OpenAI workflow, fallback itineraries, and downloadable trip plans.
+
+## Features
+
+- Guided sidebar to collect trip preferences such as destination, trip length, travel style, and special requests.
+- Generates multi-day itineraries, highlights, packing lists, and travel tips with OpenAI's `gpt-4o-mini` model.
+- Automatic fallback itinerary when an API key is not configured so the UI can be previewed locally.
+- Expandable day-by-day schedule view with dedicated tabs for packing and travel tips.
+- Download buttons for both JSON and Markdown versions of the generated itinerary.
+
+## Prerequisites
+
+- Python 3.9+
+- An OpenAI API key with access to the Responses API.
+
+## Getting started
+
+1. **Install dependencies**
+
+   ```bash
+   pip install -r requirements.txt
+   ```
+
+2. **Configure environment variables**
+
+   ```bash
+   cp .env.example .env
+   # edit .env and add your OpenAI API key
+   ```
+
+   Alternatively, export `OPENAI_API_KEY` directly in your shell or hosting platform.
+
+3. **Run the Streamlit app**
+
+   ```bash
+   streamlit run app.py
+   ```
+
+   The app will open in your browser at `http://localhost:8501`.
+
+## Usage notes
+
+- When an API key is available, the app requests a structured JSON itinerary from OpenAI. If a network or authentication issue occurs, an informative error is shown and a helpful fallback plan is displayed.
+- Use the download buttons to save the generated itinerary as JSON for integrations or Markdown for sharing with travelers.
+- Feel free to customize the prompt or add new sections (e.g., budgeting, maps) depending on your needs.
+
+## Project structure
+
+```
+.
+├── app.py              # Streamlit UI and OpenAI integration
+├── requirements.txt    # Python dependencies
+├── .env.example        # Environment variable template
+└── README.md           # Project documentation
+```
+
+## License
+
+This project inherits the MIT License from the original repository.