chore: estructura inicial del MVP

Backend (Express + MariaDB) y frontend (React + Vite, identidad Fluent/Windows) con el
nucleo funcional: seguridad, organizacion, proyectos, actividades, subtareas, dependencias,
dashboard, calendario, gantt, comentarios, adjuntos, notificaciones in-app y catalogos.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/src/modules/comments/repository.js

@@ -0,0 +1,24 @@
+import { pool } from '../../config/db.js';
+
+export async function findByEntity(entityType, entityId) {
+  const [rows] = await pool.query(
+    `SELECT c.id, c.entity_type, c.entity_id, c.user_id, u.name AS user_name, c.message, c.created_at
+     FROM comments c JOIN users u ON u.id = c.user_id
+     WHERE c.entity_type = ? AND c.entity_id = ? ORDER BY c.created_at`,
+    [entityType, entityId]
+  );
+  return rows;
+}
+
+export async function create({ entityType, entityId, userId, message }) {
+  const [result] = await pool.query(
+    'INSERT INTO comments (entity_type, entity_id, user_id, message) VALUES (?, ?, ?, ?)',
+    [entityType, entityId, userId, message]
+  );
+  const [rows] = await pool.query(
+    `SELECT c.id, c.entity_type, c.entity_id, c.user_id, u.name AS user_name, c.message, c.created_at
+     FROM comments c JOIN users u ON u.id = c.user_id WHERE c.id = ?`,
+    [result.insertId]
+  );
+  return rows[0];
+}