IAV-590/feat: Add integrations and workflow wizard steps with real-time API CRUD operations

Summary

Implement the final wizard steps (8 & 9) for integrations and workflow creation, along with migrating local state management to real-time API operations.

Changes

New Features

• Add INTEGRATIONS wizard step (step 8/9) and WORKFLOW wizard step (step 9)
• Implement createIntegration and createWorkflow API endpoints
• Add Map-based storage for created integrations with persistence
• Add workflow creation validation before wizard completion

Refactoring

• Migrate custom instructions from local state to real-time API CRUD
• Extract useStepFeaturesActions and useStepCustomInstructionsActions hooks for better separation of concerns
• Replace hardcoded userUid with dynamic retrieval from useUserStore

Technical Improvements

• Change authentication header from userUid to x-user-uid
• Add CredentialType enum and integration/workflow type definitions

Related Issue

Closes IAV-590