chore: migrate lint to ESLint CLI for Next 16

[clawgreen]

Summary

• replace removed next lint usage with ESLint CLI (pnpm exec eslint .)
• add flat ESLint config (eslint.config.mjs) based on Next core-web-vitals + typescript presets
• add ESLint dependencies compatible with Next 16 (eslint@^9, eslint-config-next)
• add temporary rule disables for react-hooks/set-state-in-effect and react/no-unescaped-entities to keep this PR scoped to lint command migration

Why

Next.js 16 removed the next lint command, so the previous script fails by treating lint as a directory argument.

Validation

• pnpm run lint now executes successfully (warnings only, no errors)

Tracking

• Refs [Atomic 03] Fix broken lint script for Next.js 16 clawgreen/terminal-ui#3

[vercel]

@clawgreen is attempting to deploy a commit to the 0xBuns Team on Vercel.

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[BunsDev]

Maintainer triage: keeping this open as a high-priority repo-health fix. The current script on still points at , which is stale for this Next 16 setup. Before merge, this branch should be refreshed against so we can validate the final lockfile and any remaining rule disables in the current tree.

[BunsDev]

Reviewed after refreshing onto current main. The lint migration is now validated against the current repo state and keeps the branch aligned with the new CI workflow.