feat(memory): implement centralized memory service for all

Summary

Implement centralized Memory Service for agent conversation isolation across all Java microservices (ADAN, ALADIN, ANIR).

Key Features:

• MemoryService interface with agent_id isolation
• MemoryServiceClient HTTP implementation (OkHttp3)
• DTOs: MemoryContextResponse, ConversationMessage
• MemoryServiceException with error details
• Comprehensive logging and validation

Changes

Added (5 Java files)

• MemoryService.java - Interface
• MemoryServiceClient.java - HTTP client (180 lines, fully documented)
• MemoryContextResponse.java - DTO
• ConversationMessage.java - DTO (OpenAI format)
• MemoryServiceException.java - Custom exception