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/server/tests/serve.rs

@@ -16,6 +16,7 @@ async fn serves_health_live_over_tcp() {
         db,
         app_name: "Test".to_string(),
         cookie_secure: false,
+        search: None,
     };
 
     let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();