Adds a new dmScope option that includes accountId in session keys,
enabling isolated sessions per channel account for multi-bot setups.
- Add 'per-account-channel-peer' to DmScope type
- Update session key generation to include accountId
- Pass accountId through routing chain
- Add tests for new routing behavior (13/13 passing)
Closes#3094
Co-authored-by: Sebastian Almeida <89653954+SebastianAlmeida@users.noreply.github.com>
