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/package.json

@@ -0,0 +1,22 @@
+{
+  "name": "@b2bcall/database",
+  "version": "0.0.1",
+  "private": true,
+  "main": "src/index.ts",
+  "types": "src/index.ts",
+  "scripts": {
+    "prisma:generate": "prisma generate",
+    "prisma:migrate": "prisma migrate dev",
+    "prisma:deploy": "prisma migrate deploy",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@prisma/adapter-pg": "^7.10.0",
+    "@prisma/client": "^7.10.0",
+    "pg": "^8.23.0"
+  },
+  "devDependencies": {
+    "@types/pg": "^8.23.1",
+    "prisma": "7.10.0"
+  }
+}