feat: add typescript monorepo with pnpm workspaces and prisma database package

- root package.json + pnpm-workspace.yaml + tsconfig.base.json
- packages/types: canonical enums (TenantStatus, AgentState)
- packages/shared: re-exports types, base for future utilities
- packages/database: Prisma 7 schema with driver adapter (pg), initial
  tenants table matching agente.md section 29, first migration applied

packages/database/prisma.config.ts

@@ -0,0 +1,8 @@
+import { defineConfig, env } from "prisma/config";
+
+export default defineConfig({
+  schema: "prisma/schema.prisma",
+  datasource: {
+    url: env("DATABASE_URL"),
+  },
+});