Split large source files into focused modules

[crankshift]

Summary

Split oversized source files into focused modules, starting with bot.js and then applying the same approach to other files that mix unrelated responsibilities.

Context

Large files make behavior harder to understand, test, and change safely. Refactoring should preserve current behavior while improving module boundaries and keeping Telegram-specific logic out of core services.

Acceptance Criteria

• Oversized files with mixed responsibilities are identified before refactoring.
• bot.js is split into cohesive modules without changing user-facing behavior.
• Other clearly oversized files are split only where the responsibility boundary is concrete.
• Tests are added or updated around moved behavior.
• Normal verification passes after the refactor.

Notes

Keep changes behavior-preserving and minimal. Follow the existing architecture boundaries in AGENTS.md.