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/pages/404.astro

@@ -8,7 +8,7 @@ Astro.response.status = 404;
   <main id="main" class="min-h-screen grid place-items-center p-4">
     <div class="w-full max-w-md text-center">
       <div class="inline-grid place-items-center w-16 h-16 rounded-[2px] bg-[color:var(--color-primary)] mb-4 p-4" style="border: 2px solid var(--color-ink); box-shadow: var(--shadow-hard);">
-        <BrandMark class="w-full h-full" />
+        <BrandMark class="w-full h-full text-white" />
       </div>
       <h1 class="text-2xl font-semibold uppercase tracking-wide">Página no encontrada</h1>
       <p class="text-sm mt-2" style="color: var(--color-pencil);">La dirección no existe o cambió de lugar.</p>

src/pages/login.astro

@@ -17,7 +17,7 @@ const googleAuthUrl = '/api/auth/signin';
     <div class="w-full max-w-md">
       <div class="text-center mb-8">
         <div class="inline-grid place-items-center w-16 h-16 rounded-[2px] bg-[color:var(--color-primary)] p-4 mb-4 motion-safe:animate-[fadein_.4s_ease-out]" style="border: 2px solid var(--color-ink); box-shadow: var(--shadow-hard);">
-          <BrandMark class="w-full h-full" />
+          <BrandMark class="w-full h-full text-white" />
         </div>
         <h1 class="text-2xl md:text-3xl font-semibold uppercase tracking-wide">Sistema de Préstamos</h1>
         <p class="text-sm mt-2" style="color: var(--color-pencil);">Laboratorio de Sistemas Computacionales · UABC</p>
@@ -29,7 +29,7 @@ const googleAuthUrl = '/api/auth/signin';
 
         <a href={googleAuthUrl} class="btn btn-primary w-full">
           <svg width="18" height="18" viewBox="0 0 48 48" aria-hidden="true" focusable="false">
-            <path fill="var(--color-ink)" d="M44.5 20H24v8.5h11.7C34.4 33.4 29.7 36 24 36c-6.6 0-12-5.4-12-12s5.4-12 12-12c2.9 0 5.5 1 7.6 2.7l6.2-6.2C33.8 5.1 29.2 3 24 3 12.4 3 3 12.4 3 24s9.4 21 21 21c11 0 20-8 20-21 0-1.4-.1-2.7-.5-4z"/>
+            <path fill="white" d="M44.5 20H24v8.5h11.7C34.4 33.4 29.7 36 24 36c-6.6 0-12-5.4-12-12s5.4-12 12-12c2.9 0 5.5 1 7.6 2.7l6.2-6.2C33.8 5.1 29.2 3 24 3 12.4 3 3 12.4 3 24s9.4 21 21 21c11 0 20-8 20-21 0-1.4-.1-2.7-.5-4z"/>
           </svg>
           Continuar con Google
         </a>