Monorepo skeleton, Prisma schema, core domain and services with tests

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

packages/core/package.json

@@ -0,0 +1,19 @@
+{
+  "name": "@barev/core",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "sideEffects": false,
+  "exports": { ".": "./src/index.ts" },
+  "scripts": {
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "zod": "^4.3.0"
+  },
+  "devDependencies": {
+    "vitest": "^4.1.0"
+  }
+}