Fix ReferenceError in todo app actions

[tanvi1107]

Description

Fixed the Todo App issue where clicking the Delete button or Clear Done button caused a ReferenceError.

Changes Made

• Attached deleteTodo, clearCompleted, addTodo, and toggleTodo functions to the global window object
• Fixed inline event handler accessibility inside the iframe preview
• Improved Todo rendering reliability

Issue Fixed

Closes #116

Testing Done

• Added new todos ✅
• Deleted todos successfully ✅
• Cleared completed todos successfully ✅
• Verified no console errors appear ✅

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[tanvi1107]

Hi maintainers @Debmallya-03
, just following up on this PR/issue.
I’ve completed the requested changes and would appreciate a review whenever possible. Thanks for your time!