Attach neume-search/pitch-search plugins to the production manuscript record

Create (if they don't already exist in production) and attach the `neume-search` and `pitch-search` Plugin records to the manuscript. Confirmed these gate which search fields the frontend shows (`OMRSearchProvider.js` checks `manuscript.isPluginActivated(...)` for these exact names) -- without them, the search panel won't show the relevant fields at all, even though the backend indexing (index_manuscript_mei) doesn't check them and will have already succeeded.

Start by reading OMRSearchProvider.js and tracing the production manuscript and Plugin records for the exact names neume-search and pitch-search. Verify the existing backend indexing path in index_manuscript_mei for context. Done means both plugins exist in production, are attached to the manuscript, and the frontend exposes the corresponding search fields.

Written by the indexing model from the issue text.