fix: pin @google/genai and google-auth-library to avoid gaxios v7 stream corruption

google-auth-library v10+ depends on gaxios v7.1.3 which has a bug:
its _request() method reads stream error bodies using Array.toString(),
which joins Buffer chunks with commas — corrupting JSON error responses
at TCP chunk boundaries. This causes TerminalQuotaError to be
misclassified due to corrupted @type fields in error details.

This fix pins:
- @google/genai to 1.30.0 (direct deps + npm override)
- google-auth-library to ^9.15.1 (direct dep + npm override)

google-auth-library v9.x uses gaxios v6.x which correctly concatenates
chunks via string addition (response += chunk).

DO NOT upgrade these packages until the gaxios v7 bug is fixed upstream.
See: #21884

Author: gsquared94