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_test.go

@@ -9,10 +9,10 @@ import (
 )
 
 func TestGetUserHabitsHandler_ReturnsAllActiveHabits(t *testing.T) {
-	habit1 := entities.NewHabit("user-123", "Exercise", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false)
+	habit1 := entities.NewHabit("user-123", "Exercise", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false, false)
 	habit1.ID = "habit-1"
 
-	habit2 := entities.NewHabit("user-123", "Read", value_objects.HabitTypeBoolean, value_objects.FrequencyWeekly, false)
+	habit2 := entities.NewHabit("user-123", "Read", value_objects.HabitTypeBoolean, value_objects.FrequencyWeekly, false, false)
 	habit2.ID = "habit-2"
 
 	habitRepo := &mockHabitRepo{habits: []*entities.Habit{habit1, habit2}}
@@ -64,7 +64,7 @@ func TestGetUserHabitsHandler_ReturnsEmptyListForUserWithNoHabits(t *testing.T)
 
 func TestGetUserHabitsHandler_IncludesAllHabitFields(t *testing.T) {
 	targetValue := 5.0
-	habit := entities.NewHabit("user-123", "Drink Water", value_objects.HabitTypeValue, value_objects.FrequencyDaily, true)
+	habit := entities.NewHabit("user-123", "Drink Water", value_objects.HabitTypeValue, value_objects.FrequencyDaily, true, false)
 	habit.ID = "habit-1"
 	habit.TargetValue = &targetValue