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_todays_habits.go

@@ -14,6 +14,7 @@ type TodaysHabitDTO struct {
 	Name          string
 	Type          value_objects.HabitType
 	TargetValue   *float64
+	IsNegative    bool
 	ScheduledDate time.Time
 	IsCarriedOver bool
 }
@@ -83,6 +84,7 @@ func (h *GetTodaysHabitsHandler) Handle(
 				Name:          habit.Name,
 				Type:          habit.Type,
 				TargetValue:   habit.TargetValue,
+				IsNegative:    habit.IsNegative,
 				ScheduledDate: query.Date,
 				IsCarriedOver: !shouldAppear && habit.CarryOver,
 			})