fix: unblock fresh clone install and docker setup

[khossdev]

What

• Use process.env['DATABASE_URL'] instead of env() in apps/api/prisma.config.ts so prisma generate (postinstall) works without a .env.
• Set real allowBuilds booleans in pnpm-workspace.yaml and remove obsolete onlyBuiltDependencies.
• Reorder README / CONTRIBUTING so .env files are created before pnpm install.
• Include prisma.config.ts in the API typecheck config.

Fixes #1

Why

A fresh clone following the docs fails before the stack can start:

1. env('DATABASE_URL') throws when unset, so pnpm install dies on Prisma postinstall.
2. allowBuilds placeholders (set this to true or false) leave builds unreviewed under pnpm 11 strictDepBuilds, so install / pnpm docker:up exit with ERR_PNPM_IGNORED_BUILDS.

Testing

• pnpm install succeeds after .env copy (Prisma client generated)
• pnpm install no longer reports ERR_PNPM_IGNORED_BUILDS (lifecycle scripts run for prisma, argon2, esbuild, etc.)
• pnpm docker:up starts the compose stack
• With .env present → pnpm db:migrate still works
• Fresh clone without .env → pnpm install still succeeds (Prisma generate only)

Screenshots

N/A — setup / config fix, no UI changes.

[Denver-sn]

Thanks @khossdev for the fix
Gg !