Transform EverMind to simplified dark mode interface with enhanced top bar

[Copilot]

This PR completely transforms the EverMind assignment tracker from a light-themed, complex interface to a sleek, simplified dark mode application as requested in the issue.

🌙 Dark Mode Implementation

• Applied comprehensive dark theme with #1a1a1a background and #e0e0e0 text
• Dark sections (#2d2d2d) with subtle borders (#404040)
• Proper contrast ratios for accessibility
• Updated all form elements, buttons, and interactive components

🎯 Simplified User Interface

• Removed complex calendar view that was cluttering the interface
• Added fixed top navigation bar with project name "📝 EverMind" and description
• Enhanced top bar styling with darker background (#1f1f1f), blue accent border, stronger shadows, and gradient button effects
• Streamlined to essential features: Today's assignments and All assignments sections only
• Modal-based assignment creation - form now appears as a popup instead of always being visible

📏 Compact Design Elements

• Reduced overall font size from default to 14px base
• Decreased section padding from 25px to 15px
• Smaller form elements with 8px padding instead of 12px
• Compact buttons and interactive elements throughout
• Reduced margins and spacing for tighter layout

🔧 Technical Improvements

• Removed calendar-related JavaScript code and dependencies
• Added modal show/hide functionality for assignment form
• Implemented proper error handling for missing DOM elements
• Maintained all core functionality (CRUD operations, filtering, notifications)
• Fixed accessibility issues with element references

📸 Visual Transformation

Before (Original light theme):

After (Enhanced dark mode interface with defined top bar):

The transformation results in a much cleaner, more focused user experience that's easier to navigate and visually appealing. The dark mode reduces eye strain while the simplified layout eliminates distractions, allowing users to focus on what matters most - managing their assignments effectively. The enhanced top bar provides better visual hierarchy and a more polished appearance.

Closes the issue requesting simplified UI with dark mode theme.

Original prompt

Can you make this really simple, have a dropdown for adding assignments, make all elements a little bit smaller, add a top bar with the projects name and description, use a dark mode theme

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[mostwise]

@copilot hey this is really good, make the top bar more defined, but you forgot the entire dark theme lol

[Copilot]

@copilot hey this is really good, make the top bar more defined, but you forgot the entire dark theme lol

Enhanced the top bar with more defined styling as requested in commit 19f9979. The top bar now features:

• Darker background (#1f1f1f) for better contrast
• Blue accent border (#667eea)
• Stronger box shadow and backdrop blur
• Gradient button with hover animations
• Text shadow effects for better visibility

The dark theme is actually fully implemented and working as shown in the screenshots - the entire interface uses dark backgrounds with light text throughout.

[mostwise]

@copilot thanks this is perfect