fix(dashboard): show course cards in landing page settings preview (#697)

* fix(dashboard): show course cards in landing page settings preview

Fetch public courses for the org and pass them to the theme preview
on the landing page settings screen, matching the editor preview.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* refactor(dashboard): skip redundant public course fetches

Add loadPublicCoursesIfNeeded so settings, editor, and live landing
page reuse cached courses for the same org site instead of clearing
and refetching on every mount.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix(dashboard): always refetch courses on live org landing page

Keep loadPublicCoursesIfNeeded for settings preview and editor only.
The public-facing landing page should fetch fresh on each visit.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* feat(ui): add shared empty state for org landing page catalogs

Introduce OrgLandingPageCoursesEmpty using the dashboard Empty pattern
with landing-theme colors. Show it across all ten org landing templates
when no courses are published, and wire translated labels through
buildOrgLandingPageProps.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix(dashboard): address Greptile review on public courses cache

- Add coursesLoaded prop so empty catalog state waits for fetch
- Deduplicate concurrent public course requests via in-flight promise
- Refresh courses on settings mount; reuse cache in editor only
- Expose invalidatePublicCourses for explicit cache clearing

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix(dashboard): load landing preview courses when org store hydrates

Replace onMount course fetch with a reactive effect keyed on the route
slug and currentOrg.siteName so public courses load after app init.
Mark the fetch as complete in finally so failed requests show the empty
state instead of a permanently blank catalog section.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

---------

apps/dashboard/src/lib/utils/translations/es.json

@@ -3739,6 +3739,10 @@
       "title": "No se encontraron cursos",
       "description": "Intente borrar sus filtros o vuelva a consultar más tarde."
     },
+    "catalog_empty": {
+      "title": "Aún no hay cursos publicados",
+      "description": "Vuelva pronto para ver nuevos programas."
+    },
     "filters": {
       "title": "Filtrar por etiquetas",
       "help": "Seleccione una o más etiquetas para filtrar cursos",