Replace ESLint with Biome

[dwjohnston]

Replaces the ESLint setup with Biome for linting.

Changes:

• Remove eslint and eslint-config-next devDependencies
• Add @biomejs/biome ^1.9.4 as devDependency
• Create biome.json with recommended rules, a11y, and formatter config
• Update lint script from eslint . to biome check .
• Remove .eslintrc.json

Closes #267

Generated with Claude Code

[dwjohnston]

@claude - This appears to be checking a bunch of generated folders. Sort out the ignore list please.

[claude]

Claude finished @dwjohnston's task in 2m 17s —— View job

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Fix Biome ignore list

• Read current biome.json
• Identify generated folders in the project
• Update biome.json ignore list
• Commit and push

Changes made

Updated biome.json with two improvements:

1. Added VCS integration — tells Biome to respect .gitignore files, which automatically excludes:

• .cache/
• .netlify/
• /public/build
• .env files
• And anything else already in .gitignore

2. Added explicit ignores for generated files not covered by .gitignore:

• next-env.d.ts — auto-generated by Next.js
• tsconfig.tsbuildinfo — TypeScript incremental build output

"vcs": {
  "enabled": true,
  "clientKind": "git",
  "useIgnoreFile": true
},

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