Convert JavaScript Codebase to TypeScript

A safe, incremental approach to converting a JavaScript codebase to TypeScript without breaking production.

## Steps:

1. Install TypeScript: npm install -D typescript @types/node @types/react (adjust for your stack)

2. Initialize tsconfig.json with allowJs: true and checkJs: false for gradual migration.

3. Start with utility files: rename .js to .ts and add type annotations.

4. Ask Copilot: 'Add TypeScript types to this module' for each file.

5. Enable strict type checking file-by-file using //@ts-check comments.

6. Convert React components: add prop types as interfaces, migrate to .tsx.

7. Update build tools (Webpack/Vite/Next.js) to handle .ts/.tsx files.

8. Gradually tighten tsconfig.json (noImplicitAny, strict mode) as coverage improves.

9. Remove allowJs once all files are migrated.

10. Run type checking in CI to prevent regressions.