Add child mode

[Josh-XT]

Add child mode. Resolves #153

This pull request introduces role-based feature restrictions, enhances audio handling with a new context-based architecture, and makes UI adjustments for child-friendly functionality. The key changes are grouped and summarized below.

Role-Based Feature Restrictions

• Added getFilteredItems function in app/NavMenuItems.tsx to filter navigation items based on user roles, specifically hiding most items for children (roleId 4).
• Introduced roleThreshold property to restrict access to specific menu items for children. [1] [2]
• Updated app/chat/[[...id]]/page.tsx and components/conversation/Message/Message.tsx to hide certain actions and features (e.g., conversation actions and message actions) from children. (app/chat/[[...id]]/page.tsxL292-R296, [1] [2]

Audio Handling Enhancements

• Replaced the AudioPlayer component with a new context-based AudioContext architecture to manage audio playback and autoplay permissions more effectively. [1] [2]
• Integrated the new AudioProvider into the app layout to ensure audio context is available globally. [1] [2] [3]

Child-Friendly UI Adjustments

• Added a ChildFriendlyVoiceRecorder component with a larger, visually appealing microphone button for children in components/conversation/input/chat-input.tsx.
• Enabled text-to-speech (tts) by default for children in components/conversation/conversation.tsx.

Markdown Media Handling

• Enhanced MarkdownLink to support audio file playback by embedding the new AudioPlayer for audio links. [1] [2]

These changes improve user experience by tailoring features and interfaces to specific user roles while modernizing audio playback capabilities.