feat: Mac-like scrollbars - thin, no track, shown while scrolling or at the edge and fading out, none when there is nothing to scroll; a lone terminal's bar sits by the frame, right of the plus

internal/server/web/templates/forwards.html

@@ -6,6 +6,7 @@
 <title>Порты · {{.Agent.Name}} - LPRA</title>
 <link rel="stylesheet" href="{{asset "app.css"}}">
 <script src="{{asset "pin.js"}}"></script>
+<script src="{{asset "scroll.js"}}" defer></script>
 <style>
   /* One line: fixed narrow fields, the label takes what is left. */
   .frow { display:flex; align-items:flex-end; gap:12px; flex-wrap:wrap; }