fix: improve type safety in media item search queries

- Change library_id parameter from interface{} to pgtype.UUID
- Add explicit UUID type casting in SQL queries
- Fix SearchMediaItemsParams to use strongly-typed UUID
- Prevents potential type assertion errors and improves type safety
- Ensures proper NULL handling for optional library_id filter

internal/database/queries/queries.sql

@@ -397,7 +397,7 @@ JOIN libraries l ON mi.library_id = l.id
 JOIN library_types lt ON l.library_type_id = lt.id
 LEFT JOIN library_visibility lv ON l.id = lv.library_id AND lv.user_id = sqlc.narg('user_id')
  WHERE COALESCE(lv.is_visible, true) = true
-   AND (sqlc.narg('library_id') IS NULL OR mi.library_id = sqlc.narg('library_id'))
+   AND (sqlc.narg('library_id')::uuid IS NULL OR mi.library_id = sqlc.narg('library_id')::uuid)
    AND (
        mi.title ILIKE sqlc.narg('search_pattern') OR
        mi.author ILIKE sqlc.narg('search_pattern') OR