build: restore build:packages on turbo 2.10.1+

[arbrandes]

Description

make build-packages fails on turbo 2.10.1 and later: without a packageManager field, turbo falls back to single-package mode and rejects the root task the packages workflow depends on. The lockfile refresh here brings that version in.

Declaring npm fixes it and makes the Makefile's package manager check flag unnecessary, which is how the other repositories on openedx/frontend-base#312 were fixed.

Part of openedx/frontend-base#312.

LLM usage notice

Built with assistance from Claude.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.19%. Comparing base (08b960d) to head (8389a96).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #27   +/-   ##
=======================================
  Coverage   74.19%   74.19%           
=======================================
  Files           6        6           
  Lines          62       62           
  Branches       10       10           
=======================================
  Hits           46       46           
  Misses         16       16           

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