feat(bigquery): add BIGQUERY_MAXIMUM_BYTES_BILLED support

[mugioka]

Summary

Upstream googleapis/mcp-toolbox#3385
wired BIGQUERY_MAXIMUM_BYTES_BILLED into the BigQuery prebuilt config.
This fix is included in v1.5.0, which is pending release
(release PR).

Tasks

• Update base image to v1.5.0 once released
• Add BIGQUERY_MAXIMUM_BYTES_BILLED to the README env var table

Variable	Required	Description	Default
BIGQUERY_MAXIMUM_BYTES_BILLED	No	Per-query bytes scanned cap. Queries exceeding this limit fail before executing.	0 (no limit)