[refactor] Improve workflow domain organization (#5584)

* [refactor] move workflow domain to its own folder

* [refactor] Fix workflow platform architecture organization

- Move workflow rendering functionality to renderer/thumbnail domain
- Rename ui folder to management for better semantic clarity
- Update all import paths to reflect proper domain boundaries
- Fix test imports to use new structure

Architecture improvements:
- rendering → renderer/thumbnail (belongs with other rendering logic)
- ui → management (better name for state management and UI integration)

This ensures proper separation of concerns and domain boundaries.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* [fix] Resolve circular dependency between nodeDefStore and subgraphStore

* [fix] Update browser test imports to use new workflow platform paths

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Co-authored-by: Claude <noreply@anthropic.com>

tests-ui/tests/utils/migration/migrateReroute.test.ts

@@ -2,7 +2,7 @@ import fs from 'node:fs'
 import path from 'node:path'
 import { describe, expect, it } from 'vitest'
 
-import type { WorkflowJSON04 } from '@/schemas/comfyWorkflowSchema'
+import type { WorkflowJSON04 } from '@/platform/workflow/validation/schemas/workflowSchema'
 import { migrateLegacyRerouteNodes } from '@/utils/migration/migrateReroute'
 
 describe('migrateReroute', () => {