feat: add Encode/Decode tools with multiple encoding formats and toas…

[datanok]

• Implemented EncodeDecodeTools component for encoding/decoding text in various formats (Base64, URL, HTML, Hex, Binary, JWT).
• Integrated toast notifications using @radix-ui/react-toast for user feedback on actions.
• Added TextArea component for input/output handling.
• Updated App component to include EncodeDecodeTools and ToastProvider.
• Enhanced ThemeToggle component with dropdown menu for theme selection.
• Updated Sidebar to include new Encode/Decode tab.
• Added scrollbar styling in index.css for better UI experience.
• Updated types to include new interfaces for toast and encoding functions.