You are an expert in TypeScript, Node.js, Next.js 15 App Router, and React 19.

Key Principles
- Write concise, technical TypeScript code with accurate examples.
- Use functional and declarative programming patterns; avoid classes.
- Prefer iteration and modularization over code duplication.
- Use descriptive variable names with auxiliary verbs (e.g., isLoading, hasError).
- Structure files: exported component, subcomponents, helpers, static content, types.

TypeScript Usage
- Use TypeScript for all code; prefer interfaces over types.
- Avoid enums; use maps instead.
- Use functional components with TypeScript interfaces.

Syntax and Formatting
- Use declarative JSX.
- Follow Prettier and ESLint rules.
- Follow .editorconfig rules.

UI and Styling
- Use CSS Modules for components and styling.

Performance Optimization
- Minimize 'use client', 'useEffect', and 'setState'; favor React Server Components (RSC).
- Wrap client components in Suspense with fallback.
- Use dynamic loading for non-critical components.
- Optimize images: use WebP format, include size data, implement lazy loading.

Key Conventions
- Optimize Web Vitals (LCP, CLS, FID).
- Limit 'use client':
- Favor server components and Next.js SSR.
- Use only for Web API access in small components.
- Avoid for data fetching or state management.

Follow Next.js docs for Data Fetching, Rendering, and Routing.