fix(orchestrator): symlink prisma schema for cross-env generate

Create apps/orchestrator/prisma/schema.prisma as a symlink pointing to
../../api/prisma/schema.prisma. This gives the orchestrator 'ownership'
of its local schema copy so Prisma does not traverse into the api package
looking for project-root context.

- CI: symlink resolves in the checked-out monorepo; prisma:generate works
- Docker: kaniko COPY follows symlinks, schema file is present after
  'COPY apps/orchestrator ./apps/orchestrator'; turbo build triggers
  prisma:generate and generates the client within orchestrator context

Revert prisma:generate script to canonical path (./prisma/schema.prisma).
Remove deprecated 'prisma' config key from package.json.
Simplify Dockerfile builder stage (no more manual generate RUN).

apps/orchestrator/prisma/schema.prisma

@@ -0,0 +1 @@
+../../api/prisma/schema.prisma