[refactor]: Optimize folder tree child name lookup in AssetManagerWindow

[coderabbitai]

Objective:
Optimize the inefficient O(n) lookup for child folder names in the AssetManagerWindow folder tree rendering to improve performance.

Acceptance Criteria:

• Modify the m_folderChildren data structure to store child names directly or implement a separate name lookup structure
• Update the drawFolderTreeItem method to retrieve child names without iterating through m_folderStructure
• Ensure the optimization maintains the same functionality and UI behavior
• Verify performance improvement through testing

Dependencies:
None

Technical Details:

Environment:

• Component: Editor
• File: editor/src/DocumentWindows/AssetManager/FolderTree.cpp (lines 62-73)

Components:

• AssetManagerWindow class
• Folder tree rendering system

Resources:

• Current implementation uses nested loop causing O(n) complexity for each child name lookup
• Suggested solution: Store FolderChild struct with path and name in m_folderChildren map

Type: Refactor

Backlinks:

• PR: fix: front-end for materials assets #344
• Comment: fix: front-end for materials assets #344 (comment)

Requested by: @iMeaNz