feat(router): add handlers for 9 new Telegram update types

Add handler functions and api.run() wiring for:

• chat_join_request: approve/decline join requests via plugins
• chat_member: member status changes (promoted, left, etc.)
• my_chat_member: bot's own status changes (added/removed/promoted)
• message_reaction: emoji reaction changes on messages
• poll: poll state changes (closed, etc.)
• poll_answer: individual user votes on polls
• chat_boost / removed_chat_boost: boost/unboost events
• message_reaction_count: anonymous reaction counts

Each handler uses a lightweight context builder (no full middleware
pipeline) and dispatches to plugin hooks following the same pcall +
error logging pattern as existing handlers.

Also fixes callback_query handler to create valid chat context for
inline button callbacks (was creating empty chat object).