fix: correct calendar navigation sticky positioning

- Fixed filter controls overlapping with hero section
- Calculate hero section height dynamically and position filters below it
- Filter controls now stick at proper position (719px from top)
- No more overlap between hero and navigation elements
- Both hero section and filters work correctly on scroll

🤖 Generated with Claude Code

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

src/pages/calendar.astro

@@ -140,7 +140,7 @@ const search = url.searchParams.get('search');
     </section>
 
     <!-- Premium Filter Controls -->
-    <section class="sticky top-0 z-50 backdrop-blur-xl shadow-2xl" data-filter-controls style="background: var(--glass-bg-lg); border-bottom: 1px solid var(--glass-border);">
+    <section class="sticky backdrop-blur-xl shadow-2xl" data-filter-controls style="background: var(--glass-bg-lg); border-bottom: 1px solid var(--glass-border); top: var(--hero-height, 0px); z-index: 45;">
       <div class="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-4">
         <div class="flex flex-col lg:flex-row items-start lg:items-center justify-between gap-4">
           <!-- View Toggle - Premium Design -->
@@ -1620,13 +1620,20 @@ const search = url.searchParams.get('search');
   // Simplified sticky header - just keep hero visible
   window.initStickyHeader = function initStickyHeader() {
     const heroSection = document.getElementById('hero-section');
+    const filterControls = document.querySelector('[data-filter-controls]');
     
-    if (!heroSection) {
+    if (!heroSection || !filterControls) {
       // If elements not found, try again in 100ms
       setTimeout(initStickyHeader, 100);
       return;
     }
     
+    // Calculate hero section height
+    const heroHeight = heroSection.offsetHeight;
+    
+    // Set CSS variable for filter controls positioning
+    document.documentElement.style.setProperty('--hero-height', `${heroHeight}px`);
+    
     // Ensure hero section stays visible with proper styling
     heroSection.style.position = 'sticky';
     heroSection.style.top = '0px';
@@ -1634,7 +1641,8 @@ const search = url.searchParams.get('search');
     heroSection.style.transform = 'translateY(0)';
     heroSection.style.opacity = '1';
     
-    console.log('Hero section initialized and kept visible');
+    console.log('Hero section initialized and kept visible. Height:', heroHeight);
+    console.log('Filter controls positioned below hero at:', `${heroHeight}px`);
   }
   
   // Initialize sticky header