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_test.go

@@ -76,7 +76,7 @@ func (m *mockEntryRepo) Delete(ctx context.Context, id string) error {
 }
 
 func TestGetTodaysHabitsHandler_DailyHabitNoEntries(t *testing.T) {
-	habit := entities.NewHabit("user-123", "Exercise", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false)
+	habit := entities.NewHabit("user-123", "Exercise", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false, false)
 	habit.ID = "habit-1"
 
 	habitRepo := &mockHabitRepo{habits: []*entities.Habit{habit}}
@@ -110,7 +110,7 @@ func TestGetTodaysHabitsHandler_DailyHabitNoEntries(t *testing.T) {
 }
 
 func TestGetTodaysHabitsHandler_DailyHabitAlreadyCompleted(t *testing.T) {
-	habit := entities.NewHabit("user-123", "Exercise", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false)
+	habit := entities.NewHabit("user-123", "Exercise", value_objects.HabitTypeBoolean, value_objects.FrequencyDaily, false, false)
 	habit.ID = "habit-1"
 
 	targetDate := time.Date(2025, 1, 15, 0, 0, 0, 0, time.UTC)
@@ -139,7 +139,7 @@ func TestGetTodaysHabitsHandler_DailyHabitAlreadyCompleted(t *testing.T) {
 }
 
 func TestGetTodaysHabitsHandler_WeeklyHabitOnCorrectDay(t *testing.T) {
-	habit := entities.NewHabit("user-123", "Gym", value_objects.HabitTypeBoolean, value_objects.FrequencyWeekly, false)
+	habit := entities.NewHabit("user-123", "Gym", value_objects.HabitTypeBoolean, value_objects.FrequencyWeekly, false, false)
 	habit.ID = "habit-1"
 	habit.SpecificDays = []int{1, 3, 5}
 
@@ -168,7 +168,7 @@ func TestGetTodaysHabitsHandler_WeeklyHabitOnCorrectDay(t *testing.T) {
 }
 
 func TestGetTodaysHabitsHandler_WeeklyHabitOnWrongDay(t *testing.T) {
-	habit := entities.NewHabit("user-123", "Gym", value_objects.HabitTypeBoolean, value_objects.FrequencyWeekly, false)
+	habit := entities.NewHabit("user-123", "Gym", value_objects.HabitTypeBoolean, value_objects.FrequencyWeekly, false, false)
 	habit.ID = "habit-1"
 	habit.SpecificDays = []int{1, 3, 5}
 
@@ -197,7 +197,7 @@ func TestGetTodaysHabitsHandler_WeeklyHabitOnWrongDay(t *testing.T) {
 }
 
 func TestGetTodaysHabitsHandler_CarryOverEnabled(t *testing.T) {
-	habit := entities.NewHabit("user-123", "Gym", value_objects.HabitTypeBoolean, value_objects.FrequencyWeekly, true)
+	habit := entities.NewHabit("user-123", "Gym", value_objects.HabitTypeBoolean, value_objects.FrequencyWeekly, true, false)
 	habit.ID = "habit-1"
 	habit.SpecificDays = []int{1}
 
@@ -230,7 +230,7 @@ func TestGetTodaysHabitsHandler_CarryOverEnabled(t *testing.T) {
 }
 
 func TestGetTodaysHabitsHandler_CarryOverDisabled(t *testing.T) {
-	habit := entities.NewHabit("user-123", "Gym", value_objects.HabitTypeBoolean, value_objects.FrequencyWeekly, false)
+	habit := entities.NewHabit("user-123", "Gym", value_objects.HabitTypeBoolean, value_objects.FrequencyWeekly, false, false)
 	habit.ID = "habit-1"
 	habit.SpecificDays = []int{1}