fix(api-client): add default settings and fix workflow update method

[vuralozsen]

Problem

1. createWorkflow fails with 'request/body must have required property settings' when settings parameter is not provided
2. updateWorkflow fails because PATCH method doesn't include all required fields, forcing users to delete and recreate workflows instead of updating them

Solution

createWorkflow Fix

• Added automatic default settings when not provided:
  • executionOrder: 'v1'
  • saveManualExecutions: true
  • callerPolicy: 'workflowsFromSameOwner'

updateWorkflow Fix

• Changed approach: now fetches existing workflow first
• Merges user updates with existing workflow data
• Uses PUT method instead of PATCH for full replacement
• Ensures all required fields are always present

Testing

• Verified workflow creation without settings parameter
• Verified workflow update (name change) without recreating
• Both operations now properly register workflows in n8n

Fixes workflow registration issues when using MCP tool