feat(trips): owner publish/unpublish toggle on /trips listing

Add an owner-only publish switch to each /trips card. It POSTs to a new
entry-actions route that mutates trip.md `published` and invalidates the
page-tree cache so the listing, nav and home reflect the change on the
next load. Owner sees drafts (Draft badge); anon/non-owner unchanged.

- U1 EntryScopeGuard::resolveTripChild — resolve a slug to a direct child
  of /trips (drafts included, for republish)
- U2 POST /api/v1/trip/{slug}/publish (setTripPublished) — owner-gated
  write, strict is_bool body, header-mutation save, audit log
- U3 trip-publish-toggle partial + CSS (role=switch, Draft badge, visible
  failure toast, ≥44px target)
- U4 owner-aware /trips listing + card restructure (toggle overlays cover
  as a non-anchor sibling; works for coverless drafts)
- U5 home active-trip branch falls back when the active trip is unpublished
- U6 trip-publish.js (confirm/pending/optimistic/revert) + esbuild wiring

Cache note: an in-place frontmatter edit keeps the folder-check cache id,
and driver:auto uses APCu in web memory, so deleteAll()+invalidateCache()
is insufficient — the endpoint also calls apcu_clear_cache().

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Mpdu3Dt1iVoozHwAMyjrbn

themes/intotheeast/templates/partials/trip-publish-toggle.html.twig

@@ -0,0 +1,27 @@
+{#
+  Owner-only publish/unpublish switch for a /trips listing card (U3, R10/R11).
+
+  Rendered by trips.html.twig as a SIBLING of the navigating card <a> (never a
+  child of it), overlaid top-right on the cover, so a click on it toggles publish
+  state rather than following the card link (KTD6). trip-publish.js binds the
+  button by `.trip-publish-toggle` and drives it from the data-* below.
+
+  Params:
+    trip      Page — the trip whose published state this controls
+    is_active bool — true when this trip is site.active_trip; drives the
+                     "home page loses it" confirm in the JS (R12)
+#}
+{% set is_active = is_active ?? false %}
+<div class="trip-publish-overlay">
+    <span class="trip-draft-badge"{% if trip.published %} hidden{% endif %}>Draft</span>
+    <button type="button"
+            class="trip-publish-toggle"
+            role="switch"
+            aria-checked="{{ trip.published ? 'true' : 'false' }}"
+            aria-label="Published — {{ trip.title }}"
+            data-trip-slug="{{ trip.slug }}"
+            data-published="{{ trip.published ? 'true' : 'false' }}"
+            data-active="{{ is_active ? 'true' : 'false' }}">
+        <span class="trip-publish-track" aria-hidden="true"><span class="trip-publish-knob"></span></span>
+    </button>
+</div>