Next.js 16 requires ESLint 9 for proper flat config support. This commit:
- Upgrades eslint from ^8 to ^9
- Migrates from .eslintrc.json to eslint.config.mjs (flat config)
- Updates lint script to use eslint directly (next lint removed in Next.js 16)
- Adds tsconfig.json includes for Next.js 16 dev types
- Fixes layout.tsx to use proper theme CSS link tags
Signed-off-by: Charles de Dreuille <charles.dedreuille@gmail.com>
Charles de Dreuille