Feature/task due time

[kaviyaa2511]

📌 Description

Added support for task due date and time using datetime-local.

🔗 Related Issue

Closes #719

🛠 Changes Made

• Replaced date input with datetime input
• Added datetime persistence while editing tasks
• Fixed datetime formatting issues in edit mode
• Fixed timezone/local datetime handling
• Updated countdown behavior to work with exact task times

Testing

• Created tasks with date and time
• Edited tasks and verified datetime persistence
• Tested countdown updates
• Verified MongoDB storage and retrieval

📸 Screenshots (if applicable)

✅ Checklist

• [Y ] Code runs locally
• [Y ] Followed project structure
• [Y] No console errors
• [Y ] Properly tested changes
• [Y ] Linked the issue

🚀 Notes for Reviewers

Implemented datetime support for task due dates using datetime-local.

Additional fixes included:

• Preserved datetime values while editing tasks
• Fixed timezone/local datetime formatting issues
• Updated countdown behavior to work with exact task times

Tested locally with:

• task creation
• task editing
• page refresh persistence
• MongoDB storage/retrieval

Some optional enhancements mentioned in the issue (such as optional start/end time and expanded dashboard time display) were intentionally left out to keep this PR focused and stable.