- Create user_settings table to store individual user preferences
- UserSettings model for get/set/delete user setting values
- Home::myProfile loads user settings with hospital defaults fallback
- Home::myProfileSave persists user settings to DB
- my_profile.php adds Sidebar Auto-Hide Delay field (0-60 seconds)
- welcome_message.php checks user settings first, then hospital default
- Setting value 0 = auto-hide disabled; blank = use hospital default
- Extensible table design for future user settings (color theme, etc)
