feat(admin-center): implement organization calculation method settings

- Added functionality to update the organization's calculation method (hourly or man-days) in the Admin Center.
- Created a new component for managing the calculation method, including UI elements for selection and saving changes.
- Updated API service to handle the new endpoint for updating the calculation method.
- Enhanced localization files to support new keys related to the calculation method settings.
- Introduced a settings page to manage organization working days and hours alongside the calculation method.

worklenz-frontend/src/components/admin-center/overview/organization-calculation-method/organization-calculation-method.tsx

@@ -0,0 +1,120 @@
+import React, { useState, useEffect } from 'react';
+import { Card, Select, Space, Typography, Tooltip, message, Button } from '@/shared/antd-imports';
+import { useTranslation } from 'react-i18next';
+import { InfoCircleOutlined, CalculatorOutlined, SaveOutlined } from '@ant-design/icons';
+import { adminCenterApiService } from '@/api/admin-center/admin-center.api.service';
+import { IOrganization } from '@/types/admin-center/admin-center.types';
+
+const { Option } = Select;
+const { Text, Title } = Typography;
+
+interface OrganizationCalculationMethodProps {
+  organization: IOrganization | null;
+  refetch: () => void;
+}
+
+const OrganizationCalculationMethod: React.FC<OrganizationCalculationMethodProps> = ({
+  organization,
+  refetch
+}) => {
+  const { t } = useTranslation('admin-center/overview');
+  const [updating, setUpdating] = useState(false);
+  const [currentMethod, setCurrentMethod] = useState<'hourly' | 'man_days'>(
+    organization?.calculation_method || 'hourly'
+  );
+  const [hasChanges, setHasChanges] = useState(false);
+
+  useEffect(() => {
+    if (organization) {
+      setCurrentMethod(organization.calculation_method || 'hourly');
+      setHasChanges(false);
+    }
+  }, [organization]);
+
+  const handleMethodChange = (newMethod: 'hourly' | 'man_days') => {
+    setCurrentMethod(newMethod);
+    setHasChanges(newMethod !== organization?.calculation_method);
+  };
+
+  const handleSave = async () => {
+    setUpdating(true);
+    try {
+      await adminCenterApiService.updateOrganizationCalculationMethod(currentMethod);
+
+      message.success(t('calculationMethodUpdated'));
+      
+      setHasChanges(false);
+      refetch();
+    } catch (error) {
+      console.error('Failed to update organization calculation method:', error);
+      message.error(t('calculationMethodUpdateError'));
+    } finally {
+      setUpdating(false);
+    }
+  };
+
+  return (
+    <Card>
+      <Space direction="vertical" size="large" style={{ width: '100%' }}>
+        <Space align="center">
+          <CalculatorOutlined />
+          <Title level={5} style={{ margin: 0 }}>
+            {t('organizationCalculationMethod')}
+          </Title>
+          <Tooltip title={t('calculationMethodTooltip')}>
+            <InfoCircleOutlined style={{ color: '#666' }} />
+          </Tooltip>
+        </Space>
+        
+        <Space direction="vertical" size="small" style={{ width: '100%' }}>
+          <Space align="center" wrap>
+            <Text strong>{t('calculationMethod')}:</Text>
+            <Select
+              value={currentMethod}
+              onChange={handleMethodChange}
+              disabled={updating}
+              style={{ width: 150 }}
+            >
+              <Option value="hourly">
+                <Space>
+                  <span>{t('hourlyRates')}</span>
+                </Space>
+              </Option>
+              <Option value="man_days">
+                <Space>
+                  <span>{t('manDays')}</span>
+                </Space>
+              </Option>
+            </Select>
+
+            {hasChanges && (
+              <Button
+                type="primary"
+                icon={<SaveOutlined />}
+                onClick={handleSave}
+                loading={updating}
+                size="small"
+              >
+                {t('saveChanges')}
+              </Button>
+            )}
+          </Space>
+
+          {currentMethod === 'hourly' && (
+            <Text type="secondary" style={{ fontSize: '12px' }}>
+              {t('hourlyCalculationDescription')}
+            </Text>
+          )}
+
+          {currentMethod === 'man_days' && (
+            <Text type="secondary" style={{ fontSize: '12px' }}>
+              {t('manDaysCalculationDescription')} ({organization?.hours_per_day}h/day)
+            </Text>
+          )}
+        </Space>
+      </Space>
+    </Card>
+  );
+};
+
+export default OrganizationCalculationMethod;