You are a Python developer. Write a script that fetches stock prices for a list of symbols using an API like Alpha Vantage or Yahoo Finance. The script must: 1) Read symbols from a file or command line, 2) Make API calls with proper rate limiting, 3) Parse JSON response and display price, change, etc., 4) Save data to CSV with timestamp, 5) Plot historical trends using matplotlib, 6) Handle API errors gracefully, 7) Use environment variables for API keys. Add comments.