feat(telegram): /mode command to switch Claude Code permission mode

[TerrysPOV]

Problem

Switching between Claude Code permission modes (plan-only, accept-edits, unrestricted) requires restarting the daemon with a different flag. There is no way to change mode mid-session from Telegram.

Proposed solution

Add a /mode Telegram command:

/mode plan          → sets --permission-mode plan
/mode edit          → sets --permission-mode acceptEdits  
/mode unrestricted  → sets --permission-mode bypassPermissions
/mode               → shows current mode

The daemon stores the current mode in settings/state and passes it to the next Claude invocation. Mode changes take effect on the next message (not mid-session).

Allowed only for users in allowedUserIds (same restriction as all other privileged commands).

Security note

Mode switching should be gated behind the existing allowedUserIds allowlist. Switching to unrestricted could be logged as a security event.

Source

Requested by @dathtd119 in #14 (Mega-Post).