Fix: Add missing CSS variables for Add to Compare button

The "Add to Compare" button on individual school pages was invisible
because the CSS variables --primary, --primary-dark, --success, and
--border-light were not defined in globals.css.

Added these variables mapped to the existing color palette:
- --primary: coral accent (#e07256)
- --primary-dark: dark coral (#c45a3f)
- --success: teal accent (#2d7d7d)
- --border-light: border color (#e5dfd5)

The button was already in the DOM but had no background color.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

nextjs-app/app/globals.css

@@ -22,6 +22,12 @@
     --accent-gold: #c9a227;
     --accent-navy: #2c3e50;
 
+    /* Button/Action colors */
+    --primary: #e07256;
+    --primary-dark: #c45a3f;
+    --success: #2d7d7d;
+    --border-light: #e5dfd5;
+    
     /* Chart colors */
     --chart-1: #e07256;
     --chart-2: #2d7d7d;