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/commands/mark_habit.go

@@ -3,10 +3,13 @@ package commands
 import (
 	"context"
 	"fmt"
+	"math"
 	"time"
 
 	"apocapoc-api/internal/domain/entities"
 	"apocapoc-api/internal/domain/repositories"
+	"apocapoc-api/internal/domain/value_objects"
+	"apocapoc-api/internal/shared/errors"
 )
 
 type MarkHabitCommand struct {
@@ -44,7 +47,61 @@ func (h *MarkHabitHandler) Handle(ctx context.Context, cmd MarkHabitCommand) err
 		return fmt.Errorf("habit is archived")
 	}
 
-	entry := entities.NewHabitEntry(cmd.HabitID, cmd.ScheduledDate, cmd.Value)
+	if habit.Type == value_objects.HabitTypeCounter && cmd.Value != nil {
+		if *cmd.Value != math.Floor(*cmd.Value) {
+			return errors.ErrInvalidInput
+		}
+	}
+
+	var finalValue *float64
+
+	if habit.Type == value_objects.HabitTypeCounter {
+		startOfDay := time.Date(cmd.ScheduledDate.Year(), cmd.ScheduledDate.Month(), cmd.ScheduledDate.Day(), 0, 0, 0, 0, cmd.ScheduledDate.Location())
+		endOfDay := startOfDay.Add(24 * time.Hour).Add(-time.Nanosecond)
+
+		existingEntries, _ := h.entryRepo.FindByHabitIDAndDateRange(ctx, cmd.HabitID, startOfDay, endOfDay)
+
+		if len(existingEntries) > 0 {
+			existingEntry := existingEntries[0]
+
+			var increment float64 = 1.0
+			if cmd.Value != nil {
+				increment = *cmd.Value
+			}
+
+			var newValue float64
+			if existingEntry.Value != nil {
+				newValue = *existingEntry.Value + increment
+			} else {
+				newValue = increment
+			}
+
+			if newValue < 0 {
+				newValue = 0
+			}
+
+			finalValue = &newValue
+			existingEntry.Value = finalValue
+			existingEntry.CompletedAt = time.Now()
+
+			return h.entryRepo.Update(ctx, existingEntry)
+		} else {
+			if cmd.Value != nil {
+				value := *cmd.Value
+				if value < 0 {
+					value = 0
+				}
+				finalValue = &value
+			} else {
+				defaultValue := 1.0
+				finalValue = &defaultValue
+			}
+		}
+	} else {
+		finalValue = cmd.Value
+	}
+
+	entry := entities.NewHabitEntry(cmd.HabitID, cmd.ScheduledDate, finalValue)
 
 	return h.entryRepo.Create(ctx, entry)
 }