refactor: Refactor styles across various components for improved conistency and aesthetics

- Adjusted padding and margins in card, comment, and container styles for better spacing. - Updated border-radius values to unify design elements. - Enhanced responsiveness and layout in friend, footer, and header styles. - Modified font sizes and line heights for better readability. - Improved scrollbar styles for mobile and desktop views. - Standardized button and notification styles for a cohesive look. - Refined widget and sidebar styles for better alignment and spacing. - Updated heat map styles for improved visual clarity. - General cleanup and optimization of CSS variables for maintainability.