v1.3.3-beta.4 ShadowOB fork

ShadowOB fork release for Shadow connector integration.\n\nChanges since beta.3:\n- Join DM channels through the current Shadow websocket channel:join event.\n- Route message:new events for known DM channels through the DM handler.\n\nIncluded from beta.3:\n- Align DM channel listing with /api/channels/dm.\n- Send DM messages through /api/channels/{id}/messages.\n- Resolve DM attachments through /api/attachments/{id}/media-url.\n- Build with no_web tag for embedded connector usage.