Add robust input validation system and fix test suite

- Add comprehensive validation package with email (RFC 5322), password strength, and IANA timezone validation
- Implement strict password requirements: min 8 chars, uppercase, lowercase, digit, special character
- Integrate validation into RegisterUserHandler with complete test coverage (59 validation tests + 25 handler tests)
- Fix pre-existing test failures:
  - Remove tests for non-existent HabitEntry.DeletedAt and Delete() methods
  - Replace deprecated HabitTypeQuantity with HabitTypeValue
  - Add missing FindByHabitIDAndDateRange mock implementation
- Remove hardcoded localhost:8080 from Swagger config for self-hosted flexibility

internal/application/queries/get_user_habits_test.go

@@ -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.HabitTypeQuantity, value_objects.FrequencyDaily, true)
+	habit := entities.NewHabit("user-123", "Drink Water", value_objects.HabitTypeValue, value_objects.FrequencyDaily, true)
 	habit.ID = "habit-1"
 	habit.TargetValue = &targetValue
 
@@ -92,8 +92,8 @@ func TestGetUserHabitsHandler_IncludesAllHabitFields(t *testing.T) {
 		t.Errorf("Expected name 'Drink Water', got %s", result.Name)
 	}
 
-	if result.Type != string(value_objects.HabitTypeQuantity) {
-		t.Errorf("Expected type %s, got %s", value_objects.HabitTypeQuantity, result.Type)
+	if result.Type != string(value_objects.HabitTypeValue) {
+		t.Errorf("Expected type %s, got %s", value_objects.HabitTypeValue, result.Type)
 	}
 
 	if result.Frequency != string(value_objects.FrequencyDaily) {