[codex] Start Intrade websocket quotes from subscriptions

[NewYaroslav]

What Changed

• Made Intrade BTC and FX websocket market-data sources subscription-driven, so live websocket quotes can start without waiting for account CONNECTED.
• Added a BTC websocket subscription refcount and default /bapi host/header setup.
• Let FX /fxconnect streams connect as soon as a public websocket subscription is added, while preserving reconnect behavior when auth host/proxy settings change.
• Wired BTC websocket source activation through MarketDataSubscriptionManager, including rollback and shutdown cleanup.
• Added local websocket-server regression tests for BTCUSDT and EUR/USD websocket tick subscriptions without publishing an account-connected event.

Why

Market-data-only use should not require the full trading authentication/connect lifecycle when the broker quote endpoints are public. The public subscription API now activates websocket quote sources directly after configuration.

Validation

• cmake --build build-codex --target intrade_bar_api_response_test -j 4
• ./build-codex/intrade_bar_api_response_test.exe --gtest_filter=IntradeBarApiResponses.BtcWebSocketSubscriptionRunsWithoutAccountConnection:IntradeBarApiResponses.FxWebSocketSubscriptionRunsWithoutAccountConnection:IntradeBarApiResponses.BtcWebSocketSubscriptionReportsStatusAndRoutesTick:IntradeBarApiResponses.FxWebSocketSubscriptionReceivesLocalTick
• ./build-codex/intrade_bar_api_response_test.exe

Notes

• This PR is stacked on [codex] Mirror Intrade bar stream status #62.
• Polling price snapshots still follow the existing connected account lifecycle; this PR only changes websocket quote sources.