Upgrade to Next.js 15 and ESLint 9

[lightwalker-eth]

Currently blocked on this: vercel/next.js#64409

Therefore keeping ESLint 8.57.1

[lightwalker-eth]

Status update: ESLint v8.x reached end-of-life on 2024-10-05 and is no longer maintained. More details:

• https://eslint.org/version-support/
• https://eslint.org/docs/latest/use/migrate-to-9.0.0

To upgrade to ESLint v9.x we will also have to upgrade all our apps to Next.js 15 to avoid peer dependency issues (see screenshot at the top of this issue). More details:

• next-lint Doesn't Support ESLint 9 vercel/next.js#64409 (comment)