refactor: add EquipmentInfo struct for cleaner equipment getter returns

[0x1NotMe]

Summary

• Introduces EquipmentInfo struct to group equipment-related return values
• Refactors equipment getter functions to use typed returns instead of multiple return values
• Improves code readability and maintainability

Changes

• Added EquipmentInfo struct to Types.sol containing:
  • itemIDs: Array of equipment IDs
  • itemNames: Array of equipment names
  • currentItemID: Currently equipped item ID
• Updated _getEquippableWeapons() to return EquipmentInfo struct
• Updated _getEquippableArmor() to return EquipmentInfo struct
• Updated pollForFrontendData() to destructure the struct values

Benefits

• Cleaner function signatures with single return value
• Better code organization by grouping related data
• Easier to extend with additional equipment metadata in the future
• Follows similar pattern to PR fix: resolve stack too deep in pollForFrontendData #11 but with more focused scope

Test plan

• Code compiles successfully
• No functional changes, only refactoring return types
• Existing tests should pass without modification