fix(post-form): style errors like 4chan and move into tfoot

Use red banner styling for form errors and render them in the table
footer so messages stay aligned with the post form layout.

src/components/post-form/post-form.module.css

@@ -236,9 +236,15 @@
 }
 
 .error {
+  display: block;
+  margin: 3px 0 0;
+  padding: 3px 5px;
+  background-color: #e62020;
+  color: #fff;
+  font-family: monospace;
+  font-size: 13px;
   font-weight: bold;
-  padding: 5px;
-  color: red;
+  line-height: normal;
 }
 
 .error a,
@@ -248,8 +254,20 @@
 }
 
 .formError {
-  margin: 8px 0;
-  padding: 6px 5px;
+  box-sizing: border-box;
+  width: 468px;
+  max-width: calc(100vw - 2px);
+  text-align: start;
+}
+
+.postFormTable .formErrorRow td {
+  width: auto;
+  padding: 0;
+  border: 0;
+  background-color: transparent;
+  color: inherit;
+  font-weight: normal;
+  text-transform: none;
 }
 
 .status {