Small fixes: gutter alignment, paste column, sort arrows, copy feedback, stats bar, title slug (#50-#55)

- #50 gutter/code line misalignment: shared --code-lh/--code-fs tokens;
  .code .gutter drops its own vertical padding (was 14px vs 0, 14px offset)
- #51 history Paste column shows only the paste name, or slug pill when untitled
- #52 sort indicator arrow sits LEFT of the column label for all sortable columns
- #53 copy buttons give in-place success feedback ('Success!' in --ok for 2s):
  paste view copy button and new-page result copy button
- #54 collapsed stats summary bar: roomier padding (14px 18px) and item gap (16px);
  wraps gracefully on mobile
- #55 paste view title bar: slug pill only shown for custom slugs, id not repeated

Closes #50, closes #51, closes #52, closes #53, closes #54, closes #55

web/templates/new.html

@@ -169,9 +169,17 @@ async function create() {
     return;
   }
   const url = location.origin + '/' + (data.custom_slug || data.id);
-  showResult('<a href="' + url + '">' + url + '</a>', false);
+  showResult('<a href="' + url + '">' + url + '</a> <button class="btn btn-icon" id="result-copy" title="Copy URL" type="button">⧉</button>', false);
   $('result').dataset.token = data.deletion_token || '';
-  try { navigator.clipboard.writeText(url); toast('Copied', 'success'); } catch(e) {}
+  const copyBtn = document.getElementById('result-copy');
+  copyBtn.addEventListener('click', () => {
+    try {
+      navigator.clipboard.writeText(url);
+      copyBtn.classList.add('ok');               // in-place success feedback (#53)
+      copyBtn.textContent = 'Success!';
+      setTimeout(() => { copyBtn.classList.remove('ok'); copyBtn.textContent = '⧉'; }, 2000);
+    } catch(e) { toast('Copy failed', 'error'); }
+  });
   const dest = '/' + data.id + '?created=1&token=' + encodeURIComponent(data.deletion_token || '');
   // password-protected: unlock now with the password we already have (#26)
   if ($('haspw').checked && data.id) {