refactor: enforce enum machine codes

Use owner enums for error and T-Bank protocol values with ESLint regression checks.

Preserve open wire fallbacks and keep protocol imports independent of DI and Prisma.

Verified npm ci, verify, 226 unit tests, 262 isolated e2e tests and unchanged OpenAPI.

src/integrations/moex/moex.client.ts

@@ -1,6 +1,8 @@
 import { Injectable, ServiceUnavailableException } from '@nestjs/common';
 import { constants as httpStatus } from 'node:http2';
 
+enum MoexErrorCode { Unavailable = 'MOEX_UNAVAILABLE' }
+
 const MIN_PRICE_PERCENT_EXCLUSIVE = 0;
 const FIRST_PAGE_OFFSET = 0;
 const EXPECTED_CURSOR_ROWS = 1;
@@ -152,7 +154,7 @@ export class MoexClient {
         pageSize === EMPTY_PAGE_SIZE ||
         current.length !== Math.min(pageSize, total - start)
       ) {
-        throw new ServiceUnavailableException({ code: 'MOEX_UNAVAILABLE' });
+        throw new ServiceUnavailableException({ code: MoexErrorCode.Unavailable });
       }
       if (index + pageSize >= total) return rows;
       start = index + pageSize;
@@ -172,22 +174,22 @@ export class MoexClient {
       }
       return body as IssResponse;
     } catch {
-      throw new ServiceUnavailableException({ code: 'MOEX_UNAVAILABLE' });
+      throw new ServiceUnavailableException({ code: MoexErrorCode.Unavailable });
     }
   }
 }
 
 function parseRows(block: IssBlock | undefined): Record<string, unknown>[] {
   if (!Array.isArray(block?.columns) || !Array.isArray(block?.data)) {
-    throw new ServiceUnavailableException({ code: 'MOEX_UNAVAILABLE' });
+    throw new ServiceUnavailableException({ code: MoexErrorCode.Unavailable });
   }
   const columns = block.columns;
   if (!columns.every((column) => typeof column === 'string')) {
-    throw new ServiceUnavailableException({ code: 'MOEX_UNAVAILABLE' });
+    throw new ServiceUnavailableException({ code: MoexErrorCode.Unavailable });
   }
   return block.data.map((values) => {
     if (!Array.isArray(values) || values.length !== columns.length) {
-      throw new ServiceUnavailableException({ code: 'MOEX_UNAVAILABLE' });
+      throw new ServiceUnavailableException({ code: MoexErrorCode.Unavailable });
     }
     return Object.fromEntries(
       // eslint-disable-next-line security/detect-object-injection -- Keys are fixed MOEX block names; row indexes come from the validated columns array.