Feature/inventory and ai cleanup

[VictorEzenma]

Description

This PR implements the requested inventory and equippable-items system, allowing items to affect player stats and progress. It also addresses
significant architectural cleanup within the src/ai-assistant domain by consolidating redundant services and migrating AI-related persistence from
Prisma to the canonical TypeORM boundary.

Key Changes

• AI Service Refactoring:
  • Consolidated redundant service implementations into src/ai-assistant/services/.
  • Migrated RagService from PrismaService to use TypeORM repositories for ContextDocument.
  • Updated AiAssistantModule to include necessary TypeORM feature providers.
• Inventory System:
  • Created Item and InventoryItem entities to manage item data and user ownership.
  • Implemented InventoryService providing robust methods for equipping/unequipping items and fetching user inventory state.
  • Registered InventoryModule in AppModule.
• Testing & Verification:
  • Added new unit tests for InventoryService to verify state transitions.
  • Updated existing AI assistant service unit tests.
  • Verified local test execution using --runInBand due to environment constraints.

Closes #278

[VictorEzenma]

Hi! I've completed the implementation for the Inventory/Equippable Items system and performed the requested architectural cleanup for the AI services.

The implementation includes:

• Consolidated AI services and migrated them to TypeORM.
• A new Inventory system (InventoryService + Item/InventoryItem entities).
• Unit tests for all new and refactored logic.

I’ve verified the changes locally, and all relevant tests are passing. Please review the PR when you have a moment. The CI pipeline should pass without issue as the test suite is now fully updated. Let me know if you need any adjustments!

[dDevAhmed]

resolve conflicts @VictorEzenma