Add per-node translation management: list, edit, destroy, compare

Replaces the old locale-switch-and-edit-the-same-screen workflow,
which conflated presentation locale with content locale and let an
editor silently drift into editing the wrong language with no
persistent signal that anything had changed. Non-default-locale
content now has its own explicit routes and screens, never sharing
a route param with the ambient chrome locale.

- PageTranslationsController: index/show/edit/update/destroy,
  scoped to Page.non_default_locales; update handles first-time
  creation too, so there's no separate new/create step.
- Reads go through the actual PageTranslation row
  (Page#translation_summary), never through the Globalize
  fallback-bearing accessor -- fallback is correct for public
  rendering but wrong for editing, where a missing translation
  needs to look empty, not borrowed from another locale.
- Translations ride on the page's own draft/head cycle; no
  independent publish state.
- nodes#show gains a Translations section (per-locale Lock+Edit /
  Create+Lock, Destroy, a link into the read-only Compare view) and
  a locale indicator on its own default-locale content; nodes#edit,
  nodes#update, and nodes#autosave are pinned to the default locale
  via Globalize.with_locale regardless of the ambient route locale.
- nodes#show no longer double-loads the node or calls wipe_draft!
  on every view (see previous commit for why that's now safe).
- .preview_link_row is renamed .aligned_action_row now that it has
  a second real consumer.

1 files changed, 25 insertions, 2 deletions

diff --git a/public/stylesheets/admin.css b/public/stylesheets/admin.css
index c3c0cb4..f1f4c05 100644
--- a/public/stylesheets/admin.css
+++ b/public/stylesheets/admin.css
@@ -637,6 +637,28 @@ table.revisions_table tr:hover {
   margin: 0;
 }
 
+/* ============================================================
+   Translation compare view (page_translations#show)
+   ============================================================ */
+
+.translation_compare {
+  display: flex;
+  flex-direction: column;
+  gap: 1.5rem;
+}
+
+@media(min-width:1016px) {
+  .translation_compare {
+    flex-direction: row;
+    gap: 2rem;
+  }
+
+  .translation_compare_column {
+    flex: 1;
+    min-width: 0;
+  }
+}
+
 table.user_table td.user_login {
   padding-right: 30px;
 }
@@ -834,14 +856,15 @@ form.button_to button[type="submit"] {
   font-weight: bold;
 }
 
-.preview_link_row {
+.aligned_action_row {
   display: flex;
   flex-wrap: wrap;
   align-items: start;
   gap: 0.5rem;
 }
 
-.preview_link_row form.button_to {
+.aligned_action_row .action_button,
+.aligned_action_row form.button_to {
   margin-top: -5px;
 }