Dark background + glowing kid cards + parent dashboard card on student home

- Student home gets a deep navy-to-indigo background so card glows pop
- Each kid card glows its own theme color via ::after blur pseudo-element with breathing animation; hover cranks it up to full brightness
- Floating school emoji opacity increased for visibility on dark bg
- 'Parent dashboard' link replaced with a frosted-glass card button

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/index.html

@@ -38,7 +38,7 @@
     <p class="subtitle">Who's learning today?</p>
     <div id="kid-cards" class="kid-cards"></div>
     <p id="no-kids" class="hint" hidden>No kids yet — a parent needs to add them.</p>
-    <a class="link-btn" href="admin.html">Parent dashboard</a>
+    <a class="parent-dash-card" href="admin.html">🔐 Parent dashboard</a>
   </section>
 
   <!-- Kid home: Today's work + nav -->