Add COUNTER type with auto-increment and IsNegative field

COUNTER type:
- Only accepts integer values (rejects decimals)
- Auto-increment behavior: each mark adds to existing value
- Supports decrement via negative values (e.g., -2)
- Enforces minimum value of 0 (never negative)
- Default increment is 1 if no value provided

VALUE type:
- Accepts decimal values
- Replaces value (no auto-increment)

IsNegative field:
- New boolean field on Habit entity
- Persisted in database (is_negative column)
- Available in all DTOs and HTTP responses
- Marks habits as "negative" (e.g., candy consumption)

Examples:
- COUNTER: 5 + (-2) = 3, 2 + (-3) = 0, 0 + (-1) = 0
- VALUE: 5000 → 12000 = 12000 (replacement)

internal/application/queries/get_user_habits.go

@@ -14,6 +14,7 @@ type HabitDTO struct {
 	Frequency    value_objects.Frequency
 	TargetValue  *float64
 	CarryOver    bool
+	IsNegative   bool
 	SpecificDays []int
 }
 
@@ -46,6 +47,7 @@ func (h *GetUserHabitsHandler) Handle(ctx context.Context, query GetUserHabitsQu
 			Frequency:    habit.Frequency,
 			TargetValue:  habit.TargetValue,
 			CarryOver:    habit.CarryOver,
+			IsNegative:   habit.IsNegative,
 			SpecificDays: habit.SpecificDays,
 		})
 	}