Add Telegram trade notifications

[MarsDoge]

Summary

• add Telegram notification fields to the auto trader and send formatted cycle summaries with reusable helpers
• load Telegram credentials from environment when building traders and shut down senders on removal
• add a unit test that verifies the generated Telegram message includes key decision data

Testing

• ⚠️ go test ./... (terminated after >2 minutes; full suite is lengthy)
• ✅ go test ./logger -run TestDecisionLogger -count=1

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Codex Task

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Prevent Telegram sender from being nilled mid-send

When Telegram notifications are enabled, removing a trader can crash the process. RemoveTrader (manager/trader_manager.go:466‑488) calls trader.Stop() and, as soon as GetStatus().is_running flips to false, immediately invokes trader.Shutdown(), which calls at.telegramSender.Stop() and sets at.telegramSender = nil. However, Stop() only toggles isRunning and closes stopMonitorCh; it does not wait for the currently running cycle to finish. If a cycle happens to be in saveAndNotifyDecision (this block) when the trader is removed, it may pass the if at.telegramSender != nil guard, build the message, and then hit at.telegramSender.SendAsync(message) after Shutdown() has already set the pointer to nil. Dereferencing a nil receiver causes a panic and tears down the goroutine (and likely the whole process). Access to telegramSender needs synchronization (e.g., take a copy before the nil check or wait for Run to exit before calling Shutdown) so the pointer cannot change between the guard and the method call.

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