Refactor: Centralize Prisma schema and restrict DB access

This commit refactors the project to use a shared Prisma schema and restricts direct database access to the API service.

Key changes:

- Created a new shared package `core/prisma` containing the Prisma schema, generated client, and types.
- Configured the monorepo to use NPM workspaces, including `core/prisma` and all services.
- Updated all services (`api`, `ui`, `mcp`, `agent`, and the background processing service) to depend on `@empresa/prisma-schema`.
- The API service now imports `PrismaClient` from `@empresa/prisma-schema/client`.
- Other services import only types from `@empresa/prisma-schema`.
- Removed redundant Prisma configurations from `api` and the background processing service.
- Updated the background processing service's `sync-empleados.js` to fetch data via an API call instead of direct database access.
- Updated TypeScript configurations (`tsconfig.base.json` and service-specific ones) to support the new structure and path aliases.
- Updated `README.md` to reflect the new architecture and added convenience scripts for Prisma operations.

This change promotes a single source of truth for data models, reduces code duplication, and improves the overall architecture by centralizing database operations within the API service.

api/server.js

@@ -1,6 +1,5 @@
 import express from 'express';
-import { PrismaClient } from './prisma/generated/client/index.js';
-import { Decimal } from '@prisma/client/runtime/library.js';
+import { PrismaClient } from '@empresa/prisma-schema/client';
 import cors from 'cors';
 
 // Import new routers
@@ -16,7 +15,6 @@ import planillasRouter from './routes/planillas/planillas.js';
 // Resto del código
 
 BigInt.prototype.toJSON = function () { return this.toString(); };
-Decimal.prototype.toJSON = function () { return this.toString(); };
 
 const prisma = new PrismaClient();
 export const app = express();