Remove unnecessary comments from codebase

Clean up obvious and redundant comments that don't add value:
- Remove step-by-step comments in command handlers
- Remove obvious test setup comments
- Keep only meaningful comments that explain why, not what

internal/application/commands/update_habit.go

@@ -30,28 +30,23 @@ func NewUpdateHabitHandler(habitRepo repositories.HabitRepository) *UpdateHabitH
 }
 
 func (h *UpdateHabitHandler) Handle(ctx context.Context, cmd UpdateHabitCommand) error {
-	// Validate input
 	if strings.TrimSpace(cmd.Name) == "" {
 		return errors.ErrInvalidInput
 	}
 
-	// Find existing habit
 	habit, err := h.habitRepo.FindByID(ctx, cmd.HabitID)
 	if err != nil {
 		return err
 	}
 
-	// Check ownership
 	if habit.UserID != cmd.UserID {
 		return errors.ErrUnauthorized
 	}
 
-	// Cannot update archived habits
 	if !habit.IsActive() {
 		return errors.ErrInvalidInput
 	}
 
-	// Update fields
 	habit.Name = cmd.Name
 	habit.Description = cmd.Description
 	habit.CarryOver = cmd.CarryOver
@@ -59,6 +54,5 @@ func (h *UpdateHabitHandler) Handle(ctx context.Context, cmd UpdateHabitCommand)
 	habit.SpecificDays = cmd.SpecificDays
 	habit.SpecificDates = cmd.SpecificDates
 
-	// Save changes
 	return h.habitRepo.Update(ctx, habit)
 }