Add bottom margin to embeds in compose box

- Added mb-3 to embed containers for spacing before toolbar
- Ensures proper visual separation between embedded content and action buttons

Co-authored-by: shakespeare.diy <assistant@shakespeare.diy>

src/components/ComposeBox.tsx

@@ -319,7 +319,7 @@ export function ComposeBox({ onSuccess, placeholder = "What's on your mind?", co
 
         {/* Quoted event preview */}
         {showQuotedEvent && quotedEvent && quotedEventKey && (
-          <div className="relative mt-4">
+          <div className="relative mt-4 mb-3">
             <button
               onClick={() => setRemovedEmbeds(prev => new Set(prev).add(quotedEventKey))}
               className="absolute top-2 right-2 z-10 p-1.5 rounded-full bg-background/80 backdrop-blur-sm border border-border text-muted-foreground hover:text-foreground hover:bg-background transition-colors"
@@ -333,7 +333,7 @@ export function ComposeBox({ onSuccess, placeholder = "What's on your mind?", co
 
         {/* Detected embeds */}
         {visibleEmbeds.map((embed, i) => (
-          <div key={`${embed.type}-${i}`} className="relative mt-4">
+          <div key={`${embed.type}-${i}`} className="relative mt-4 mb-3">
             <button
               onClick={() => setRemovedEmbeds(prev => new Set(prev).add(embed.value))}
               className="absolute top-2 right-2 z-10 p-1.5 rounded-full bg-background/80 backdrop-blur-sm border border-border text-muted-foreground hover:text-foreground hover:bg-background transition-colors"