feat: add Telegram, Inbox, and URL Watchers

[vaheed]

Summary

Adds Telegram support plus a small proactive layer for OpenDots: an Inbox and public-URL Watchers.

What changed

• Adds an optional Telegram channel using @copilotkit/channels/telegram
• Supports long-polling by default and optional webhook mode
• Requires an explicit TELEGRAM_USER_IDS allowlist before Telegram can invoke a Dot
• Supports selecting a dedicated TELEGRAM_DOT_ID
• Reports Telegram channel status in Settings & setup
• Adds a persistent Inbox for completed/failed background work and watcher triggers
• Adds URL Watchers that establish a content baseline and queue a normal task when the public page changes
• Watchers support pause/resume/delete and intervals from 1 minute to 24 hours
• Watcher fetching rejects local/private destinations, URL credentials, oversized responses, and excessive redirects
• Adds unit coverage for Telegram wiring plus Inbox/Watcher persistence
• Leaves the existing managed Slack integration intact

Verification

I reviewed the implementation against the existing OpenDots task/conversation architecture and the current CopilotKit Channels Telegram adapter.

The local sandbox cannot reliably run the full npm test/build suite because external package/network access is unavailable, so executable validation is left to GitHub CI. The current PR check/status APIs report no completed check run yet.