Add Place Related Orders to contingent order types

[AlexCatarino]

Every contingency type can trigger follow-up orders, so each type page gets a Place Related Orders section after Place Orders:

• Bracket Orders: the built-in exits can't trigger orders, so the section builds the bracket from order factory parts, with a take profit that triggers a re-entry (a grandchild of the entry).
• One Triggers Other Orders: the chain and grandchild content moves here from Place Orders.
• One Cancels Other Orders: two breakout entries that cancel each other, each with its own bracket.
• One Updates Other Orders: a stop loss that triggers a reversal.

The later sections move from 03-08 to 04-09. Nothing linked to their anchors. Custom Contingent Orders › Relate Order Requests gets an Examples column that links each method to the matching section. Bracket Orders also gets Example 2, where the take profit triggers a re-entry.

The new code uses the order factory from QuantConnect/Lean#9828, so the example isn't marked testable yet.

Test plan

• docs-style linter passes on all Contingent Orders pages, and the renumbered .php sections render without warnings.
• Checked the trigger and cancel rules in the Add contingent orders: OCO, OTO, OUO and brackets Lean#9828 OrderContingency.Relate, ContingentOrderProcessor, and BacktestingBrokerage.