Implement Habit Dependencies

[A23droid]

Description

Allow habits to have dependencies so that some habits can only be marked complete after prerequisite habits are completed.
This feature enforces logical chains and encourages disciplined tracking.

Acceptance Criteria

• Users can assign prerequisite habits.
• A habit cannot be marked complete unless prerequisites are fulfilled.
• UI clearly indicates locked habits due to unmet dependencies.
• Circular dependency attempts are prevented and handled gracefully.