DuckDB BigQuery extension defaults `bq_query_timeout_ms` to 90 s, which
is too tight for analyst-scale queries against view-backed BQ datasets.
`agnes query --remote` HTTP 400'd with `Binder Error: Query execution
exceeded the timeout. Job ID: ...` whenever the underlying BQ job ran
longer than 90 s, even though the job itself was healthy.
Add `data_source.bigquery.query_timeout_ms` (default 600 000 ms = 10 min,
sentinel 0 falls through to the extension default). Applied via
`SET bq_query_timeout_ms` after every `LOAD bigquery` on every BQ-touching
DuckDB session: orchestrator's `_remote_attach` ATTACH path, BqAccess
session factory, and the standalone extractor. Configurable via
`/admin/server-config` UI.
Fail-soft: extension versions that don't recognise the setting silently
keep the default rather than poisoning the session.
