docs: document query.timeout duration key alongside query.timeout.sec

[PedroHenrique0713]

What

Documents the query.timeout configuration key on the Cairo engine reference page, next to the existing query.timeout.sec, and clarifies how the two relate.

Why

Part of #274, which reports the query timeout configuration as inconsistent. The root cause is a documentation gap: both keys are valid and related, but no page explains that.

From the source (PropServerConfiguration.java):

this.queryTimeout = (long) (getDouble(properties, env, PropertyKey.QUERY_TIMEOUT_SEC, "60") * Micros.SECOND_MILLIS);
this.queryTimeout = getMillis(properties, env, PropertyKey.QUERY_TIMEOUT, this.queryTimeout);

• query.timeout.sec — a number of seconds (default 60)
• query.timeout — a duration parsed by Numbers.parseMillis (e.g. 120s, 1m, 500ms) that overrides query.timeout.sec when set

Today the reference page (configuration/cairo-engine.md) only lists query.timeout.sec, while the configuration overview example uses query.timeout=120s. Neither mentions the other, which is what makes the two look inconsistent. This change makes the reference document both keys so the pages agree.

Scope

This addresses the query.timeout point of #274 only. The other two points look out of scope for this docs repo:

• cairo.auto.scale.symbol.capacity — its default changed in feat(sql): enable symbol capacity auto-scaling by default questdb#6352, so it is better covered by the broader config refresh mentioned in the issue thread.
• line.tcp.auth.db.path — already documented in configuration/ingestion.md; the "missing from the default config" note is about the generated server.conf template in the core repo, not these docs.

Testing

Docs-only prose change with no new links or components, so the Docusaurus broken-link build covers it.