chore: simplify js commands + scripts

[synoet]

Simple package.json scripts.
bun run {dev,build,test,check,preview,lint,format,fix,clean}
all work as expected.

• Simplified the package.json scripts to be just core commands
• Fixed check, fix, format, test commands to work correctly
• All convenience / helper scripts moved to justfile.
• Justfile in ci

[github-actions]

Preview: https://synoet-simplify-commmands-qto3ob.preview.macro.com (4bce0a9)