feat: add system workflow webhook events

[huanghongbo-hhb]

Summary

• Add system-level workflow webhook settings for workflow start and completion events

Why

• Support a global workflow webhook entry in system settings without introducing callback behavior
• Reuse the existing workflow notification webhook payload so external integrations receive consistent task data

Main Changes

• Add workflow_hook system settings with enable, hook_address, hook_secret, and hook_events
• Add system APIs to get and update workflow webhook settings
• Trigger system workflow webhooks on workflow start and workflow completion
• Reuse the existing workflow notification payload and include workflow.event_name to distinguish start_execute and complete_execute
• Add a unit test for workflow hook event filtering

Risk / Compatibility

• Low risk because this is additive and gated by a new system setting
• Existing workflow notification hooks are unchanged
• The new webhook path reuses the current workflow payload shape, with only an additional event_name field for the system workflow hook scenario

Test

• go test -vet=off ./pkg/microservice/aslan/core/common/service/instantmessage
• go test -vet=off ./pkg/microservice/aslan/core/common/service/instantmessage ./pkg/microservice/aslan/core/common/service/workflowcontroller ./pkg/microservice/aslan/core/system/handler ./pkg/microservice/aslan/core/system/service ./pkg/microservice/aslan/core/workflow/service/workflow

Contact

• Contact: huanghongbo@koderover.com

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