feat(notes): an Archive button in the open note's footer

Archiving a single note meant finding its row in the list and its hover-only
button. With a note open to read or write, the one place you would reach for it —
its own footer, beside Gem and Slet — had no way to put it away.

There is one now: Arkivér between Save and Delete, which reads "bring it back" once
the note is already archived. Owner only, like delete, and it runs the same archive
the row button does — the note leaves the list without leaving the account.

e2e: archiving from the footer takes the note off the list, the archive holds it
with a bring-back button, and bringing it back returns it. The existing bulk-archive
test is scoped to the selection bar, now that "Arkivér" also lives in the footer.

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

web/src/routes/noter/+page.svelte

@@ -1036,6 +1036,12 @@
 
 					<button class="button" onclick={save}>{t('notes.save')}</button>
 					{#if ownsSelected}
+						<!-- Laid away, not thrown away: archive is the note leaving the list
+						     without leaving the account, and it reads "bring it back" once it
+						     already has. Owner only, like delete. -->
+						<button class="button" onclick={() => archiveOne(selected)}>
+							{selected.archived_at ? t('notes.unarchive') : t('notes.archive')}
+						</button>
 						<button class="button danger" onclick={() => remove(selected)}>{t('notes.delete')}</button>
 					{/if}
 				</div>