Update pricing model to include half-year pricing and enhance validation

- Introduced a new pricing field, `PricePerConfigPerHalfYear`, to the `PricingSettings` model, allowing for more flexible pricing options.
- Updated the `UpdatePricingSettingsCommand` and its validator to include the new half-year pricing, ensuring proper validation against the quarterly and yearly rates.
- Modified the `PricingSettingsDto` and related frontend components to accommodate the new half-year pricing field, including validation logic to prevent pricing discrepancies.
- Enhanced API documentation and frontend forms to reflect the updated pricing structure and validation rules.

frontend/src/routes/admin/roles.tsx

@@ -74,7 +74,7 @@ function AdminRolesPage() {
                 <td className="py-2">{role.maxConfigs < 0 ? t('unlimited') : role.maxConfigs}</td>
                 <td className="py-2">{role.maxIpLimit < 0 ? t('unlimited') : role.maxIpLimit}</td>
                 <td className="py-2">{totalPrice(pricing?.pricePerConfigPerQuarter, role.maxConfigs, 3)}</td>
-                <td className="py-2">{totalPrice(pricing?.pricePerConfigPerQuarter, role.maxConfigs, 6)}</td>
+                <td className="py-2">{totalPrice(pricing?.pricePerConfigPerHalfYear, role.maxConfigs, 6)}</td>
                 <td className="py-2">{totalPrice(pricing?.pricePerConfigPerYear, role.maxConfigs, 12)}</td>
                 <td className="py-2 text-right">
                   <Button size="sm" variant="outline" onClick={() => setEditing(role)}>