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/infrastructure/persistence/sqlite/habit_repository_test.go

@@ -130,9 +130,9 @@ func TestHabitRepositoryFindActiveByUserID(t *testing.T) {
 
 	userID := "user-789"
 
-	habit1 := entities.NewHabit(userID, "Habit 1", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false)
-	habit2 := entities.NewHabit(userID, "Habit 2", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false)
-	habit3 := entities.NewHabit(userID, "Habit 3", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false)
+	habit1 := entities.NewHabit(userID, "Habit 1", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false, false)
+	habit2 := entities.NewHabit(userID, "Habit 2", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false, false)
+	habit3 := entities.NewHabit(userID, "Habit 3", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false, false)
 
 	repo.Create(ctx, habit1)
 	repo.Create(ctx, habit2)