Document Webull brokerage

[AlexCatarino]

Summary

Adds documentation for the Webull brokerage (QuantConnect/Lean#9362), following the Charles Schwab structure and inserting Webull immediately after Charles Schwab in each section (renumbering the brokerages that follow):

• Cloud Platform › Live Trading › Brokerages › 08 Webull
• Reality Modeling › Brokerages › Supported Models › 08 Webull
• Lean CLI › Live Trading › Brokerages › 08 Webull
• Transaction Fees › Supported Models › 18 Webull Model (alphabetical)
• Shared Resources/brokerages/webull/*, introduction-by-brokerage/webull.html, create-credentials/webull.html
• Live-deploy API schema: WebullBrokerageSettings in QuantConnect-Platform-2.0.0.yaml and the Create Live Algorithm request
• Lean CLI supported-brokerages list

Webull is an execution-only brokerage (US Equities, Equity Options, and Index Options) with no live data feed, so it is intentionally not added to the data-provider listings. The brokerage pages direct users to the QuantConnect data provider (cloud) or Polygon (local) for market data.

Key details sourced from the Lean/Lean.Brokerages.WeBull implementation: order types (Market, Limit, StopMarket, StopLimit; TrailingStop for equity only), WebullOrderProperties.OutsideRegularTradingHours, Day/GTC time-in-force rules, App Key/App Secret/Account ID authentication, commission-free equity/options with tiered index-option fees, and rate limits.

Test plan

• Verified the four renumbered sections have no duplicate/missing numbers and Webull lands at the correct position.
• QuantConnect-Platform-2.0.0.yaml parses as valid YAML; all new/edited metadata.json and 00.json files parse as valid JSON.
• Confirmed no dangling references to a (non-existent) Webull dataset page.
• Render the affected pages in the docs preview to confirm layout (tables, code tabs, links).