Dark Mode & UI Improvements

This PR adds dark mode support to Devise views and improves overall UI organization.

Dark Mode Support

• Added dark mode styling across all Devise views
• Enhanced error_messages partial with proper dark mode colors
• Updated password reset views with dark mode compatibility
• Fixed styling in all Devise templates to support dark mode
• Add dark mode preference detection on top of app preference

Improved Table Navigation

• Converted "My Assignments" List/Table views to a tabbed interface
• Created scrollable containers that utilize available viewport height
• Applied sticky positioning to table headers in Table View
• Made date headers in List View sticky as well
• Added appropriate background colors to ensure sticky headers remain visible

User Profile Enhancements

• Grouped appearance settings (Theme Preference and Profile Color)
• Added better labels and helpful descriptions for settings
• Created a collapsible "Change Password" section (hidden by default)
• Made "More Languages Team only" section collapsible and collapsed by default
• Implemented measures to prevent browser autocomplete on password fields

enabled an automatic merge when all merge checks for d82c5e9e pass

merged

mentioned in commit 218c8fcd

mentioned in merge request !27 (merged)

Dark mode still doesn't work quite as well as before:

• Changing the preference in the settings requires a reload before taking effect
• Toggling the browser preference overrides the setting, even if not set to "auto"