Refactor: Adaptar componentes base al sistema de temas

Cambios:
- app.vue: Reemplazar #fef9f0 con var(--brand-text)
- layouts/dashboard.vue: Usar var(--brand-text)
- layouts/informe.vue: Usar var(--brand-text)

Todos los componentes base ahora responden al sistema de temas.

nuxt4-app/app/app.vue

@@ -1,6 +1,6 @@
 <template>
   <UApp>
-    <div class="brand-shell text-[#fef9f0]">
+    <div class="brand-shell text-[var(--brand-text)]">
       <NuxtRouteAnnouncer />
       <NuxtLayout>
         <NuxtPage />

nuxt4-app/app/layouts/dashboard.vue

@@ -1,5 +1,5 @@
 <template>
-  <div class="brand-shell min-h-screen text-[#fef9f0]">
+  <div class="brand-shell min-h-screen text-[var(--brand-text)]">
   <UDashboardGroup storage-key="analytics-dashboard" class="h-full">
     <AppSidebar />
 

nuxt4-app/app/layouts/informe.vue

@@ -1,5 +1,5 @@
 <template>
-  <div class="brand-shell min-h-screen text-[#fef9f0]">
+  <div class="brand-shell min-h-screen text-[var(--brand-text)]">
     <UDashboardGroup storage-key="analytics-dashboard" class="h-full">
       <AppSidebar />