feat: Add UTM tracking params to BrainGrid partner banner link

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

Author: davila7

dashboard/src/components/PartnerBanner.astro

@@ -4,7 +4,7 @@
 
 <section class="px-6 pt-4 pb-1">
   <a
-    href="https://www.braingrid.ai"
+    href="https://www.braingrid.ai?utm_source=aitmpl&utm_medium=banner&utm_campaign=partner"
     target="_blank"
     rel="noopener noreferrer"
     class="group relative flex items-center gap-3 overflow-hidden rounded-lg border border-border bg-surface-1 px-4 py-3 transition-all hover:border-border-hover"