feat(api): implement inventory API endpoints

Add REST API endpoints for character inventory management:
- GET /api/v1/characters/<id>/inventory - Get inventory and equipped items
- POST /api/v1/characters/<id>/inventory/equip - Equip item to slot
- POST /api/v1/characters/<id>/inventory/unequip - Unequip from slot
- POST /api/v1/characters/<id>/inventory/use - Use consumable item
- DELETE /api/v1/characters/<id>/inventory/<item_id> - Drop item

All endpoints include:
- Authentication via @require_auth decorator
- Ownership validation through CharacterService
- Comprehensive error handling with proper HTTP status codes
- Full logging for debugging

Includes 25 integration tests covering authentication requirements,
URL patterns, and response formats.

Task 2.4 of Phase 4 Combat Implementation complete.

.gitignore

@@ -35,3 +35,4 @@ Thumbs.db
 logs/
 app/logs/
 *.log
+CLAUDE.md