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/ui-context.jsx

@@ -0,0 +1,65 @@
+import { createContext, useContext, useEffect, useMemo, useState, useCallback } from 'react';
+import { messages } from '../i18n/messages.js';
+
+const UiContext = createContext(null);
+
+function readStored(key, fallback) {
+  try {
+    return localStorage.getItem(key) || fallback;
+  } catch {
+    return fallback;
+  }
+}
+
+export function UiProvider({ children }) {
+  const [theme, setThemeState] = useState(() => readStored('plc_theme', 'dark'));
+  const [lang, setLangState] = useState(() => readStored('plc_lang', 'es-EC'));
+  const [buttonMode, setButtonModeState] = useState(() => readStored('plc_button_mode', 'icon-text'));
+  const [dialog, setDialog] = useState(null);
+  const [toasts, setToasts] = useState([]);
+
+  useEffect(() => {
+    document.documentElement.setAttribute('data-theme', theme);
+    localStorage.setItem('plc_theme', theme);
+  }, [theme]);
+
+  useEffect(() => {
+    document.documentElement.setAttribute('lang', lang);
+    localStorage.setItem('plc_lang', lang);
+  }, [lang]);
+
+  useEffect(() => {
+    document.documentElement.setAttribute('data-button-mode', buttonMode);
+    localStorage.setItem('plc_button_mode', buttonMode);
+  }, [buttonMode]);
+
+  const t = useCallback((key) => messages[lang]?.[key] ?? messages['es-EC'][key] ?? key, [lang]);
+
+  const openDialog = useCallback((config) => setDialog(config), []);
+  const closeDialog = useCallback(() => setDialog(null), []);
+
+  const pushToast = useCallback((toast) => {
+    const id = Date.now() + Math.random();
+    setToasts((prev) => [...prev, { id, tone: 'info', ...toast }]);
+    setTimeout(() => setToasts((prev) => prev.filter((t2) => t2.id !== id)), 4000);
+  }, []);
+
+  const value = useMemo(
+    () => ({
+      theme, setTheme: setThemeState,
+      lang, setLang: setLangState,
+      buttonMode, setButtonMode: setButtonModeState,
+      t, dialog, openDialog, closeDialog,
+      toasts, pushToast,
+    }),
+    [theme, lang, buttonMode, t, dialog, openDialog, closeDialog, toasts, pushToast]
+  );
+
+  return <UiContext.Provider value={value}>{children}</UiContext.Provider>;
+}
+
+export function useUi() {
+  const ctx = useContext(UiContext);
+  if (!ctx) throw new Error('useUi debe usarse dentro de UiProvider');
+  return ctx;
+}