Updates SearchMediaItemsUnified to conditionally set LibraryID parameter
only when it's valid. Previously, the code always set LibraryID in the
dbParams struct, which caused pgx to pass a zero UUID instead of NULL
to PostgreSQL.
New behavior:
- Only sets dbParams.LibraryID when params.LibraryID.Valid is true
- When library_id is empty, LibraryID is omitted from the struct
- Go's zero value + pgx's "field not set" detection = NULL in SQL
Also fixes type mismatches in SearchFieldValues method where
SearchQuery parameter needed explicit pgtype.Text wrapping with
Valid=true flag for proper nullable text handling.
This ensures that omitting the library_id query parameter results in
searching across all libraries, not filtering by zero UUID.
john-okeefe
bd3057ec80