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>

frontend/src/context/auth-context.jsx

@@ -0,0 +1,44 @@
+import { createContext, useContext, useEffect, useMemo, useState, useCallback } from 'react';
+import { api, setUnauthorizedHandler } from '../services/api.js';
+
+const AuthContext = createContext(null);
+
+export function AuthProvider({ children }) {
+  const [user, setUser] = useState(null);
+  const [ready, setReady] = useState(false);
+
+  const logout = useCallback(() => {
+    api.setToken(null);
+    setUser(null);
+  }, []);
+
+  useEffect(() => {
+    setUnauthorizedHandler(() => logout());
+  }, [logout]);
+
+  useEffect(() => {
+    const token = localStorage.getItem('plc_token');
+    if (!token) { setReady(true); return; }
+    api.get('/auth/me')
+      .then((me) => setUser(me))
+      .catch(() => logout())
+      .finally(() => setReady(true));
+  }, [logout]);
+
+  const login = useCallback(async (email, password) => {
+    const result = await api.post('/auth/login', { email, password });
+    api.setToken(result.token);
+    setUser(result.user);
+    return result.user;
+  }, []);
+
+  const value = useMemo(() => ({ user, ready, login, logout }), [user, ready, login, logout]);
+
+  return <AuthContext.Provider value={value}>{children}</AuthContext.Provider>;
+}
+
+export function useAuth() {
+  const ctx = useContext(AuthContext);
+  if (!ctx) throw new Error('useAuth debe usarse dentro de AuthProvider');
+  return ctx;
+}