fix: make 'Tag' label bold in Edit Task screen

[mulikruchi07]

Description

This PR updates the "Tag" label styling in the Edit Task screen to use a bold font weight. Other labels in the screen already use bold text, so this change improves UI consistency and readability

Fixes #(issue_no)

No issue was opened for this change since it is a small UI fix.

Screenshots

Checklist

• Tests have been added or updated to cover the changes
• Documentation has been updated to reflect the changes
• [ x ] Code follows the established coding style guidelines
• [ x ] All tests are passing

[Copilot]

Pull request overview

This PR improves UI consistency in the Edit Task screen by making the "Tag" label bold to match the styling of other labels. The implementation follows the codebase's ongoing migration from GoogleFonts.poppins() to using TextStyle with the generated FontFamily.poppins constant.

• Converts the Tag label from a simple Text widget to a RichText widget with separate styling for the label and value
• Applies bold font weight to the label portion while keeping the tag values in regular weight
• Uses FontFamily.poppins and TaskWarriorFonts constants, consistent with the migration pattern seen in description_widget.dart

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