Back up unsaved editor work locally, structure the settings, fix archive accessibility

- The editor keeps unsaved changes in the browser and offers them
  after a crash, a closed tab or an expired session. No timed save on
  the server: every save is a full revision.
- The save status stays visible in narrow windows.
- Settings get a sticky section bar, two folded groups and a save bar
  that stays in view.
- The admin post list fetches terms and images once, not per post.
- Archive post titles are second-level headings, the archive head
  keeps full text contrast, the skip link sits above a sticky header,
  a linked image without alternative text names its link.
- The editor check starts through the dev router like the others.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

public/assets/admin.css

@@ -1165,3 +1165,19 @@ details.form-card > summary.form-card-summary::before, details.form-card[open] >
 .confirm-dialog .dialog-actions .primary, .confirm-dialog .dialog-actions .secondary { margin: 0 }
 .primary.danger { background: var(--danger); border-color: var(--danger) }
 .primary.danger:hover:not(:disabled) { background: #6f251b; border-color: #6f251b }
+/* ---- Lange Formulare: Sprungleiste, Klappbereiche, stehende Speicherleiste (Einstellungen) ---- */
+.jump-nav { position: sticky; top: 0; z-index: 6; display: flex; flex-wrap: wrap; gap: 6px; margin: 0 -4px 6px; padding: 10px 4px; background: color-mix(in srgb, var(--bg, #f3f5f1) 92%, transparent); backdrop-filter: blur(6px) }
+.jump-nav a { display: inline-flex; align-items: center; min-height: 32px; padding: 4px 12px; border: 1px solid var(--line); border-radius: 999px; background: var(--paper); color: var(--ink); font-size: 12.5px; font-weight: 600; text-decoration: none }
+.jump-nav a:hover { border-color: var(--accent) }
+.stack-section[id], .section-head h2[id] { scroll-margin-top: 64px }
+.field-fold > summary { display: flex; align-items: baseline; justify-content: space-between; gap: 12px; padding: 12px 0 8px; font-weight: 700; cursor: pointer; list-style: none }
+.field-fold > summary::-webkit-details-marker { display: none }
+.field-fold > summary::before { content: ''; flex: none; width: 7px; height: 7px; margin-right: 2px; border-right: 2px solid currentColor; border-bottom: 2px solid currentColor; transform: translateY(-2px) rotate(-45deg) }
+.field-fold[open] > summary::before { transform: translateY(-3px) rotate(45deg) }
+.field-fold > summary .muted { margin-left: auto; font-size: 12px; font-weight: 500 }
+.field-fold:not([open]) { padding-bottom: 4px }
+.form-save-bar { position: sticky; bottom: 0; z-index: 5; display: flex; flex-wrap: wrap; align-items: center; gap: 8px 16px; margin: 22px -22px -24px; padding: 14px 22px; border-top: 1px solid var(--line); border-radius: 0 0 12px 12px; background: color-mix(in srgb, var(--paper) 94%, transparent); backdrop-filter: blur(6px) }
+.card-body .form-save-bar .primary { margin: 0 }
+.form-save-bar .muted { font-size: 12px }
+@media (prefers-reduced-motion: no-preference) { html { scroll-behavior: smooth } }
+@media (max-width: 700px) { .jump-nav { flex-wrap: nowrap; overflow-x: auto; scrollbar-width: none } .jump-nav a { flex: none } .form-save-bar .muted { display: none } }