IAV-583/feat(iavia-common): Add integration management DTOs and orchestration service support

Summary

This MR introduces the foundation for user and agent integration management in iavia-common, enabling the orchestration service to handle platform integrations (Slack, Teams, Telegram, etc.) across agents.

Changes

New Enumerations

• IntegrationCredentialSource: Distinguishes between USER_PROVIDED (real credentials) and SYSTEM_GENERATED (placeholder credentials)
• MainAgentWizardStep: Defines the steps for the agent configuration wizard (WELCOME → RESUME)

New DTOs

• Credential DTOs: CredentialPropertyDTO, CredentialTypeSchemaDTO for credential schema definitions
• Request DTOs: CreateUserIntegrationRequestDTO for creating integrations with optional inline credential creation
• Response DTOs: AgentIntegrationResponseDTO, AgentIntegrationListResponseDTO (with pagination), UserIntegrationResponseDTO

Service Configuration

• Added orchestration service URL in NameUrl (port 8092)
• Added IAVIA_ORCHESTRATION path constant in NameUri
• Added agent integration endpoint builders in OrchestrationServicePath

Entity Updates

• Extended CustomerCareAgent with credential source fields for: WhatsApp, Instagram, Facebook Messenger, Telegram, Shopify, WooCommerce, Freshdesk

Closes IAV-583