chore: cleanup unused files and docs

[satnaing]

Description

This PR cleans up the project structure by removing unused files and updating documentation to match the current codebase.

Changes

• Remove unused asset: Deleted public/assets/forrest-gump-quote.webp which was not referenced anywhere in the codebase
• Reorganize type declarations: Moved remark-collapse.d.ts from root to src/ directory for better organization
• Update documentation: Fixed README.md project structure section to:
  • Remove outdated references to non-existent public/assets/ directory
  • Remove outdated reference to public/toggle-theme.js (functionality moved to src/scripts/theme.ts)
  • Fix duplicate entries and improve tree structure formatting
  • Add src/scripts/ directory to the structure

Types of changes

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Documentation Update (if none of the other choices apply)
• Others (any other types not listed above)

Checklist

• I have read the Contributing Guide
• I have added the necessary documentation (if appropriate)
• Breaking Change (fix or feature that would cause existing functionality to not work as expected)

Further comments

Related Issue

Closes #609