Give destruction its own colour, take ember back

The stylesheet asserted twice that --ember only ever means "new chapter" while
spending it on eight things, including "Nothing new." — the heat signal firing
on its own negation.

Add a --danger token (a duller oxblood, tuned per theme) and move remove hover,
the open remove cell, the confirm wash and the login error onto it. Text-input
focus follows the .searchbar idiom and turns --paper, so a valid number field
no longer paints itself red. Drop .empty.hot. Ember now survives on the is-new
group, the Updated tab and the brand, which the law comment now says out loud.

Contrast, both themes: --danger on --ink 4.82 dark / 6.65 light, --danger-ink
on the solid button 4.94 / 7.30, --danger-soft on the wash 9.00 / 7.98.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/templates/list.html

@@ -11,7 +11,7 @@
 {{else if eq .Tab "fav"}}
   <div class="empty"><strong>No favourites yet.</strong><p>Star a series to pin it here.</p></div>
 {{else if eq .Tab "new"}}
-  <div class="empty hot"><strong>Nothing new.</strong><p>Every series is caught up to its latest chapter.</p></div>
+  <div class="empty"><strong>Nothing new.</strong><p>Every series is caught up to its latest chapter.</p></div>
 {{else if eq .Tab "archived"}}
   <div class="empty"><strong>Nothing archived.</strong><p>Shelve a series to park it here — it keeps getting checked for new chapters.</p></div>
 {{else if eq .Tab "finished"}}