DRY pass #2, batch 5, F14: the web's repeated class lists become component classes (#5372)

style.css gains the classes the views spelled out in full: .section-label
(17 sites), .hint (20), .form-error (13), .alert-error (5), .row-card (5),
.list-empty (5), .field (5), .page-shell (3), and the small row action
.btn-sm (4) / .btn-sm-danger (3). Only exact runs moved, so nothing renders
differently; spacing a site adds beyond a run stays a utility beside it.

Kept: the Reminders and Timeline small buttons. They carry no text colour
and inherit it, so putting them on .btn-sm would recolour them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/components/NoteEditor.vue

@@ -761,7 +761,7 @@ function revPreview(rev: NoteRevision): string {
           v-if="!isCreate && showHistory"
           class="flex flex-col gap-1 border-t border-neutral-100 pt-2 dark:border-neutral-800"
         >
-          <p class="text-xs font-semibold uppercase tracking-wide text-neutral-400">History</p>
+          <p class="section-label">History</p>
           <p v-if="!revisions.length" class="text-xs text-neutral-400">
             No earlier versions yet — your edits will show up here.
           </p>