appview/pages: remove `@` from AtLink extension

we now prefer links with `@`. this change also moves the styling into
the mention class entirely.

Signed-off-by: oppiliappan <[e-mail]>

appview/pages/markup/extension/atlink.go

···
 
 func (r *atHtmlRenderer) renderAt(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
 	if entering {
-		w.WriteString(`<a href="/@`)
+		w.WriteString(`<a href="/`)
 		w.WriteString(n.(*AtNode).Handle)
-		w.WriteString(`" class="mention font-bold">`)
+		w.WriteString(`" class="mention">`)
 	} else {
 		w.WriteString("</a>")
 	}

input.css

···
         }
 
         .prose a.mention {
-            @apply no-underline hover:underline;
+            @apply no-underline hover:underline font-bold;
         }
 
         .prose li {