Redesign comments into glass bubble format

- Top-level comments render as glass-card bubbles with subtle
  border, backdrop blur, and hover highlight
- Replies use a lighter, more compact bubble variant
- Threaded replies connected by a vertical line on the left
  instead of raw margin indentation
- Action buttons (upvote, downvote, reply, expand) styled as
  pill-shaped micro-buttons inside each bubble
- Reply form nests inline within the parent bubble
- Proper spacing and responsive padding at all nesting depths

Co-authored-by: Cursor <cursoragent@cursor.com>

src/components/ContentDetailModal.vue

@@ -177,8 +177,8 @@
                 <div class="text-white/40 text-sm">No comments yet. Be the first!</div>
               </div>
 
-              <!-- Threaded comments -->
-              <div v-else class="space-y-1">
+              <!-- Threaded comments (bubble layout) -->
+              <div v-else class="space-y-2">
                 <template v-for="node in commentTree" :key="node.event.id">
                   <CommentNode
                     :node="node"