feat: add Discord community runtime and gateway transport

[lev-goryachev]

Summary

• add the Discord community bot runtime foundation, including connector abstractions, automation engine/executor modules, CRM/message ingestion helpers, and guild mapping cache support
• introduce the first Redis-backed Discord gateway transport for hosted onboarding, plus gateway proxy connectors and shared action handlers
• update Discord onboarding to run on the hosted gateway path and surface channel permission diagnostics instead of silent failures

Test plan

• static Python compile checks on touched client-kit files
• local gateway service startup and Redis command-path smoke checks
• local end-to-end onboarding smoke test through the hosted gateway path
• reviewer pass on connector contract stability for future non-Discord adapters
• reviewer pass on rollout plan for remaining Discord-only hooks (reaction roles, checklist, announce)