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/styles/global.css

@@ -2,7 +2,7 @@
 @import "@fontsource-variable/jetbrains-mono";
 
 @theme {
-  /* MotherDuck-derived palette, remapped to LabPréstamos' semantics */
+  /* MotherDuck-derived system (shadow/radius/type mechanics); identity colors are UABC's own */
   --color-cream: #f4efea;
   --color-frost: #ffffff;
   --color-chalk: #f8f8f7;
@@ -12,10 +12,11 @@
   --color-pencil: #a1a1a1;
   --color-graphite: #818181;
 
-  --color-primary: #6fc2ff;
-  --color-primary-hover: #56b4f7;
-  --color-secondary: #ff9538;
-  --color-secondary-hover: #ef8526;
+  /* UABC institutional green/gold — dark enough that primary needs white text, not charcoal */
+  --color-primary: #00723F;
+  --color-primary-hover: #005f34;
+  --color-secondary: #DD971A;
+  --color-secondary-hover: #c78614;
   --color-danger: #f38e84;
   --color-danger-hover: #ec7469;
   /* AA-contrast text variant of Coral Sketch — the fill color reads ~2:1 on white, too light for body text */
@@ -57,7 +58,7 @@
   }
   ::selection {
     background: var(--color-primary);
-    color: var(--color-ink);
+    color: white;
   }
   /* Tabular data keeps real square corners even where a nested control forgets to ask */
   table {
@@ -88,10 +89,10 @@
   }
   .btn-primary {
     background: var(--color-primary);
-    color: var(--color-ink);
+    color: white;
   }
   .btn-secondary {
-    background: var(--color-frost);
+    background: var(--color-secondary);
     color: var(--color-ink);
   }
   .btn-ghost {