chore(lint): add stricter ESLint rules and update existing code

[TheauW]

I added new ESLint rules and updated the existing codebase to comply with them. The new rules include:

• Disallow usage of any
• Disallow import * as Module from 'module'
• Disallow unused imports
• Disallow unreachable code
• Disallow unused variables
• Enforce consistent indentation

Some additional minor rules were also added.