feed: fix nesting layout bug

under some circumstances the reply-to lines on 3rd level did not
correctly visualize the nesting of the thread.

fixed and added links to test cases.

src/styles/cards.css

@@ -124,8 +124,8 @@ a.mbox-img:focus {
 .mbox-replies .mbox-replies .mbox-replies {
   --reply-padding: 0;
 }
-/* direct replies */
+/* direct replies, test with http://localhost:8001/note1aer8780aywqqlfgjjch75uqmkujcdj4edv009nuludwq7w46lkvssclaxx */
-.mbox-replies .mbox-replies .mbox::before {
+.mbox-replies .mbox-replies .mbox:first-child::before {
   background: none;
   border-color: var(--bgcolor-inactive);;
   border-style: solid;
@@ -172,8 +172,9 @@ a.mbox-img:focus {
 .mbox-has-replies .mbox:not(:last-child) > .mbox-body::after {
   left: -33px;
 }
+/* test with http://localhost:8001/note1aer8780aywqqlfgjjch75uqmkujcdj4edv009nuludwq7w46lkvssclaxx */
 .mbox-has-replies .mbox-has-replies .mbox:not(:last-child) > .mbox-body::after {
-  left: -36px;
+  left: -18px;
 }
 .mbox-has-replies > .mbox-body::after {
   left: -33px;
@@ -188,8 +189,9 @@ a.mbox-img:focus {
 .mbox-replies .mbox-has-replies:not(:last-child)::after {
   left: 19px;
 }
+/* test with http://localhost:8001/note1quq9waqtrgl97v3gutg4au4zthetz853u8knsnz65nrqhavxvq8qrp6lyg */
 .mbox-replies .mbox-replies .mbox-has-replies:not(:last-child)::after {
-  left: -11px;
+  left: 7px;
 }
 
 .mbox-replies .mbox-replies .mbox-has-replies > .mbox-body::after {