fix: set Slack mode to 'http' when no SLACK_APP_TOKEN (default)

Add Slack channel support (Socket Mode + HTTP)

Increase timeouts to 3600s (1 hour)

Increase all timeouts from 180s to 600s (10 min max)

nv provider: use localhost proxy (bypass CF worker timeout)

Fix UND_ERR_INVALID_ARG: strip dispatcher from ALL fetch calls + use NVIDIA API directly

Increase timeouts: provider 180s, telegram 180s, agent 180s

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