feat: telegram bot command receiver (closes #135)

[luceinaltis]

Summary

Adds inbound command receiving via the Telegram getUpdates long-polling API so users can interact with qracer remotely from chat. Builds on the existing TelegramAdapter — stdlib urllib only, no new dependencies.

• New TelegramBotPoller in qracer/notifications/telegram_poller.py:
  • Long-polls getUpdates, tracks the update offset so messages are never returned twice.
  • Filters by the authorised chat_id (other chats are silently ignored).
  • Parses incoming text into BotCommand objects.
  • send_reply() posts plain-text replies, auto-truncating to fit Telegram's per-message limit (default 4000 chars).
  • All HTTP/JSON errors are caught, logged, and converted to an empty result so the server tick keeps running.
• New BotCommand dataclass with a parse(text) classmethod that strips the @botname suffix groups append (e.g. /analyze@qracerbot AAPL) and lower-cases the action.
• Server gains an optional telegram_poller constructor param. _tick() polls when configured (failures are logged, never raised) and calls _handle_bot_command for each command, replying via poller.send_reply.
• Commands implemented in Server._dispatch_bot_command:
  • /help (and /start) — usage text
  • /status — uptime, notification channels, autonomous on/off
  • /alerts — list active alerts via the existing AlertStore
  • /alert TICKER above|below PRICE — create a price alert
  • /tasks — list active scheduled tasks via the existing TaskStore
  • /schedule ACTION TICKER SCHEDULE — schedule a task (e.g. /schedule analyze AAPL every 1h)
  • /analyze and /portfolio — reply with a friendly "use the qracer CLI" message; deeper engine plumbing for these is out of scope for this issue.
  • Unknown commands fall through to a /help hint.
• build_telegram_poller factory in qracer/notifications/factory.py mirrors build_notification_registry and returns None when credentials are missing.
• cli serve instantiates the poller from TELEGRAM_BOT_TOKEN / TELEGRAM_CHAT_ID and announces "Telegram bot: receiving commands" at startup.

Closes #135.

How to test it

Automated:

uv run pytest tests/notifications tests/test_server.py
uv run ruff check qracer/ tests/
uv run ruff format --check qracer/ tests/

I added 30 unit tests for the poller (tests/notifications/test_telegram_poller.py) covering:

• BotCommand.parse happy paths and rejection cases (empty, whitespace, non-slash, lone slash, /@bot).
• Construction validation (missing token / chat id).
• poll() parsing, offset tracking, chat-id filtering, non-text message skipping, non-command-text skipping.
• Offset is sent on subsequent calls.
• HTTP / URL / JSON / ok=false errors all return [] without raising.
• send_reply() success, truncation, empty-text short-circuit, HTTP / URL errors.

I extended tests/test_server.py with 22 tests covering:

• _tick polls Telegram when configured, skips when not, dispatches commands and replies.
• Poll failures and dispatch exceptions are caught and produce an error reply (not a crash).
• Each _cmd_* handler in isolation, plus _format_duration.

Manual smoke test (requires real bot):

export TELEGRAM_BOT_TOKEN=...   # from @BotFather
export TELEGRAM_CHAT_ID=...     # your chat id
qracer serve
# In Telegram, message your bot:
/help
/status
/alerts
/alert AAPL above 200
/tasks
/schedule analyze AAPL every 1h

You should see each command echoed back as a reply within ~1s of sending.