Fix: texto blanco sobre verde institucional en elementos rellenos

El verde UABC (#00723F) es demasiado oscuro para texto carbón (~2:1,
falla AA). Corrige BrandMark, nav activo (sidebar/dock), chip de
FiltroCategorias y botón de Google en login a texto/ícono blanco
(~6.2:1). Actualiza DESIGN.md/PRODUCT.md y design.json acorde.

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

src/layouts/AppLayout.astro

@@ -64,7 +64,7 @@ const activeCheck = (item: NavItem) => {
     <aside id="app-sidebar" class="hidden md:flex md:fixed md:top-0 md:left-0 md:w-64 md:h-screen bg-white text-[color:var(--color-ink)] md:flex-col md:z-40 sidebar-panel transition-transform duration-200 ease-out" style="border-right: 2px solid var(--color-ink);">
       <a href="/" class="p-6 flex items-center gap-3 focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-[color:var(--color-ink)]" aria-label="LabPréstamos — Inicio" style="border-bottom: 2px solid var(--color-ink);">
         <div class="w-9 h-9 rounded-[2px] bg-[color:var(--color-primary)] grid place-items-center p-2" style="border: 2px solid var(--color-ink);" aria-hidden="true">
-          <BrandMark class="w-full h-full" />
+          <BrandMark class="w-full h-full text-white" />
         </div>
         <div>
           <div class="font-semibold leading-tight uppercase tracking-wide text-sm">LabPréstamos</div>
@@ -77,7 +77,7 @@ const activeCheck = (item: NavItem) => {
             href={item.href}
             class:list={[
               'flex items-center gap-3 px-3 py-2.5 rounded-[2px] text-sm font-medium uppercase tracking-wide whitespace-nowrap transition-colors',
-              activeCheck(item) ? 'bg-[color:var(--color-primary)]' : 'hover:bg-[color:var(--color-chalk)]'
+              activeCheck(item) ? 'bg-[color:var(--color-primary)] text-white' : 'hover:bg-[color:var(--color-chalk)]'
             ]}
             style={activeCheck(item) ? 'border: 2px solid var(--color-ink);' : 'border: 2px solid transparent;'}
             aria-current={activeCheck(item) ? 'page' : undefined}
@@ -154,7 +154,7 @@ const activeCheck = (item: NavItem) => {
             <span
               class:list={[
                 'grid place-items-center rounded-[2px] w-11 h-11 transition-[background-color,transform] duration-100 motion-safe:active:scale-95',
-                active ? 'bg-[color:var(--color-primary)]' : ''
+                active ? 'bg-[color:var(--color-primary)] text-white' : ''
               ]}
               style={active ? 'border: 2px solid var(--color-ink);' : ''}
             >