fix(orchestrator): add prisma CLI as devDependency for prisma:generate script

The prisma:generate script added in #703 calls 'prisma generate' but the
prisma CLI was not installed in the orchestrator package. Adding it as a
devDependency so pnpm can resolve it during the monorepo build step.

apps/orchestrator/package.json

@@ -47,6 +47,7 @@
     "@types/express": "^5.0.1",
     "@types/node": "^22.13.4",
     "@vitest/coverage-v8": "^4.0.18",
+    "prisma": "^6.19.2",
     "ts-node": "^10.9.2",
     "tsconfig-paths": "^4.2.0",
     "typescript": "^5.8.2",