feat(api): on-write search reindex after catalogue writes (#17)

Wire best-effort Meilisearch index sync into the admin write paths
(create/update/delete/set_fields/set_visibility). Adds
SearchClient::sync_object (reindex if the object exists, remove if gone —
one uniform path), an optional AppState.search client, and a reindex
helper that logs failures via tracing without failing the committed
write. Server gains MEILI_URL/MEILI_MASTER_KEY/MEILI_INDEX config;
search stays disabled (no-op) when unset. reindex_all remains the
recovery path.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/api/src/admin.rs

@@ -160,6 +160,8 @@ pub(crate) async fn set_visibility(
                 .await
                 .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
 
+            crate::reindex(&state, object_id).await;
+
             Ok(StatusCode::NO_CONTENT)
         }
         Err(db::catalog::VisibilityError::ObjectNotFound) => Err(StatusCode::NOT_FOUND),