fix(channel): return success when bind code is re-checked by same identity

[0x24a]

Problem

When binding a user identity via Telegram, the bot returns "Bind code already used" even though the binding process has succeeded in the database.

Root Cause

IdentityResolver.Resolve() is being called twice for each inbound message: by the middleware layer and HandleInbound. The second response overwrites the first, so the user only sees the error.

Fix

Add a check in tryHandleBindCode, When a bind code has already been used, check if it was used by the same channel identity. If yes, then return the success reply instead of an error.