Enhance MarkdownText with LaTeX support

[samrudha01codespace]

This pull request significantly enhances the MarkdownText composable in MarkdownText.kt by adding LaTeX math expression support and improving Markdown rendering. It introduces a helper for converting common LaTeX math to Unicode, processes inline math in Markdown, and adds previews and theming improvements. The changes also refactor imports and update styling for better integration with the app's theme.

LaTeX and Math Rendering Enhancements:

• Added a convertLatexToUnicode helper function to translate common LaTeX math expressions (Greek letters, operators, superscripts, subscripts, fractions) into Unicode equivalents. This enables basic math rendering within Markdown content.
• Updated the MarkdownText composable to process and replace inline LaTeX expressions (e.g., `$...
  ) with their Unicode representations before rendering.
• Added a MathExpression composable for rendering block and inline math with appropriate styling, though only inline math is currently handled in the Markdown.

UI and Theming Improvements:

• Updated code block and link styling within Markdown to use the app’s theme colors and improved padding and font settings for better readability.
• Switched to using OfflineLLMTheme and reorganized the file’s import structure for consistency with the rest of the app. [1] [2]

Developer Experience:

• Added new preview composables (MarkdownTextPreview, SimpleTutorialButton) to showcase Markdown with math examples and demonstrate the new features in the UI.

Refactoring and Cleanup:

• Removed unused or outdated code, such as the old preview and references to the previous theme system.

File Organization:

• Moved the file to the com.genzopia.offlineai.Design package and updated the package declaration accordingly.