Update codebase to work with Next.js 16 breaking changes:

- Remove unused `res` parameter from API route handlers (App Router
  only accepts request parameter)
- Update page props to use Promise types for params/searchParams
- Use React's use() hook to unwrap async props in client components
- Rename middleware.ts to proxy.ts (Next.js 16 naming convention)
- Make Clerk auth calls async with await
- Add --webpack flag to dev/build scripts (opt out of Turbopack)
- Update tsconfig.json for Next.js 16 compatibility

Affected components:
- 6 API routes (create-interview, generate-insights, register-call,
  generate-interview-questions, get-call, response-webhook)
- 2 dynamic pages (interviews/[interviewId], call/[interviewId])
- Middleware/proxy configuration
- Build configuration