New Features

• Add environment variable support for all global arguments
  • DUA_THREADS → --threads
  • DUA_FORMAT → --format
  • DUA_APPARENT_SIZE → --apparent-size
  • DUA_COUNT_HARD_LINKS → --count-hard-links
  • DUA_STAY_ON_FILESYSTEM → --stay-on-filesystem
  • DUA_IGNORE_DIRS → --ignore-dirs
  • DUA_LOG_FILE → --log-file
• Mark shared arguments as global for general accessibility
  • Added global = true to all arguments shared between aggregate and interactive subcommands
  • Removed duplicate input fields from Interactive and Aggregate subcommands
  • Updated main.rs to use opt.input instead of subcommand-specific input
  • Global arguments now work with both subcommands and can be specified before or after the subcommand