feat(ipsec): add certificate export functionality by name

- Implemented a new backend route for exporting existing client certificates in .p12 format by name.
- Enhanced the frontend to support exporting certificates directly from the IPsec server grid.
- Updated the IPsec page to manage certificate states and handle exports effectively.
- Introduced new utility functions for certificate handling and improved data structures to accommodate the changes.
- Added tests to ensure the reliability of the new certificate export feature.

packages/contracts/src/certificates.ts

@@ -25,6 +25,8 @@ export const certificateDtoSchema = z.object({
   trusted: z.boolean(),
   status: certStatusSchema,
   acmeStatus: z.string().optional(),
+  /** Имя CA, которым серт подписан на устройстве (read-only поле `ca` RouterOS). */
+  signedByCertName: z.string().optional(),
 })
 
 export const certificatesListResponseSchema = z.object({