feat: add nested comment reply indicators and responsive flat-reply styling

Add `comment-reply-to` span showing parent author with ↳ indicator in comment headers, and introduce `.comment-replies-flat` dashed border style for deeply nested threads. Adjust responsive spacing: reduce comment gap and vote min-width on mobile, hide reply-to indicator on small screens, and increase reply padding for better readability.

devplacepy/static/css/post.css

@@ -91,6 +91,15 @@
     border-left: 2px solid var(--border);
 }
 
+.comment-replies-flat {
+    border-left-style: dashed;
+}
+
+.comment-reply-to {
+    font-size: 0.75rem;
+    color: var(--text-muted);
+}
+
 .comment-votes {
     display: flex;
     flex-direction: column;
@@ -137,6 +146,7 @@
 .comment-header {
     display: flex;
     align-items: center;
+    flex-wrap: wrap;
     gap: 0.5rem;
     margin-bottom: 0.25rem;
 }
@@ -219,16 +229,21 @@
     }
 
     .comment {
-        gap: 0.5rem;
+        gap: 0.375rem;
         margin-left: calc(var(--comment-depth, 0) * 0.025rem);
     }
 
     .comment-votes {
-        min-width: 28px;
+        min-width: 24px;
     }
 
     .comment-replies {
-        padding-left: 0.025rem;
+        margin-top: 0.5rem;
+        padding-left: 0.5rem;
+    }
+
+    .comment-reply-to {
+        display: none;
     }
 }
 
@@ -240,4 +255,16 @@
     .comments-section {
         padding: var(--space-md);
     }
+
+    .comment {
+        gap: 0.25rem;
+    }
+
+    .comment-votes {
+        min-width: 20px;
+    }
+
+    .comment-replies {
+        padding-left: 0.375rem;
+    }
 }