feat: telegram multi-chat broadcast + broker fixes

[fprivitera]

Summary

• Telegram multi-chat broadcast: register one TelegramConnector per allowed chat ID; first uses channel 'telegram', subsequent use 'telegram:<chatId>' to avoid overwriting the primary
• Heartbeat: switched from connectorCenter.notify() to connectorCenter.broadcast() so all registered Telegram chats receive delivery
• Config: z.coerce.number() for chatIds so string values from env/JSON are accepted without error
• Trading brokers: fixes in AlpacaBroker, CcxtBroker, TradingGit with expanded test coverage (72 new lines in AlpacaBroker.spec)

Test Plan

• All 877 tests pass (pnpm test)
• Verify heartbeat delivers to multiple Telegram chats simultaneously
• Verify chatIds accepts string values in config (e.g. from env vars)
• Smoke-test AlpacaBroker and CcxtBroker order flows

🤖 Generated with Claude Code

[luokerenx4]

Hey Filippo, thanks for the effort — these are real bugs and it's clear you've actually been running OpenAlice.

A few notes:

Already fixed upstream: The Decimal rehydration crash (qty.equals is not a function) and the Alpaca notional priority issue were both fixed on master the day before this PR (see d2df072 and 696a6ae). The master fix takes a more thorough approach — TradingGit.restore() now rebuilds Decimal instances directly rather than defensive type-checking at call sites. Your fork may be behind; syncing with upstream should pick these up.

Multi-chat broadcast: The Telegram group/multi-chat feature is intentionally not implemented yet. Alice is currently a single-tenant agent — adding group chat support would rapidly escalate permission management complexity (who can trigger trades? who sees portfolio data? per-chat session isolation?). It's on the radar but not something we can add in the short term.

Project policy: We don't accept external PRs for security reasons — OpenAlice executes real financial operations and we need full control over the code surface. See CONTRIBUTING.md for details. That said, bug reports and feature requests via issues are very welcome!