refactor: migrate TelegramAdapter to grammY and remove Telegraf

[shepherdwind]

Background

Task 005 of the grammY migration plan. The main integration task — remove Telegraf dependency and wire everything through grammY.

Approach

Rewrite TelegramAdapter to use grammY Bot, register conversations and command handlers, and delete all Telegraf-specific code.

Changes

Deleted (7 files, ~1200 lines removed):

• command-handlers.ts — replaced by grammY middleware chain
• base-command-handler.ts — no longer needed
• add-command-handler.ts — replaced by addBill conversation
• categorization-command-handler.ts — replaced by categorization conversation
• categorization-utils.ts, categorization-types.ts — internalized
• categorization-command-handler.test.ts — handler deleted

Modified:

• telegram.adapter.ts — full rewrite using grammY Bot, conversations, short ID registry
• query-command-handler.ts — removed BaseCommandHandler dependency
• custom-query-command-handler.ts — removed BaseCommandHandler dependency
• conversations/categorization.ts — use short ID registry for merchant lookup, cleanup on all exit paths
• types.ts — removed Telegraf TextMessage type
• package.json — removed telegraf dependency

Key design:

• Short ID hashing for callback data (Telegram 64-byte limit)
• Pending merchant registry (Map) for conversation data lookup
• All categorization exit paths clean up registry to prevent leaks

Testing

39 tests pass (7 suites). No Telegraf imports remain in codebase.

Code Review

• Review tool: Codex
• Rounds: 3 (max)
• Issues fixed: (1) preserve merchant metadata in notifications (P1), (2) short ID hashing for callback data limit (P1), (3) registry cleanup on all exit paths (P2), (4) bot.start() fire-and-forget with onStart callback (P1)