Add ESLint + Prettier + TypeScript strict mode

[trsdn]

Summary

Set up code quality tooling foundation for consistent code style and stricter type checking.

Tasks

• Add ESLint with TypeScript plugin
• Add Prettier for code formatting
• Create \ sconfig.json\ with strict mode enabled
• Add lint/format npm scripts
• Add .eslintrc.js\ and .prettierrc\ config files
• Fix any existing linting errors

Acceptance Criteria

• 
  pm run lint\ runs ESLint successfully
• 
  pm run format\ formats all files with Prettier
• TypeScript strict mode catches type issues at compile time
• Pre-commit hook (optional) runs lint/format