UI improvements: collapsible schedule menu and fix double extensions

• Hide schedule section in collapsible menu on upload screen (collapsed by default)
• Fix download filenames to prevent double extensions like .zip.zip
• Use PicoCSS details/summary for clean collapsible interface

russell@unturf.com is the boss

Summary by CodeRabbit

• New Features

  • Added a collapsible section for "Scheduled Actions (Optional)" in the upload media form, allowing users to show or hide scheduling options for improved usability.

• Bug Fixes

  • Improved download filename logic to prevent duplicate file extensions when downloading media files.

• Documentation

  • Added project instructions for commit message formatting, including requirements and an example message.