feat(web): archived and finished tabs with per-card status controls

backend/templates/list.html

@@ -5,6 +5,10 @@
   <p class="empty">No favourites yet. Star a series to pin it here.</p>
 {{else if eq .Tab "new"}}
   <p class="empty">Nothing new. Every series is caught up to its latest chapter.</p>
+{{else if eq .Tab "archived"}}
+  <p class="empty">Nothing archived. Shelve a series to park it here — it keeps getting checked for new chapters.</p>
+{{else if eq .Tab "finished"}}
+  <p class="empty">Nothing finished yet.</p>
 {{else}}
   <p class="empty">
     Nothing here yet. Bookmarks appear once the userscript records a chapter.