Move "Show past" toggle

Move the "Show past conferences" toggle to below the conference category filter bar.

src/pages/Index.tsx

@@ -59,7 +59,7 @@ const Index = () => {
     <div className="min-h-screen bg-neutral-light">
       <Header />
       <div className="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8">
-        <div className="flex items-center justify-between py-4">
+        <div className="space-y-4 py-4">
           <FilterBar selectedTag={selectedTag} onTagSelect={setSelectedTag} />
           <div className="flex items-center gap-2">
             <label htmlFor="show-past" className="text-sm text-neutral-600">