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/tbank/instrument-metadata.service.ts

@@ -12,6 +12,7 @@ import {
   TbankAccessService,
   type TbankSyncAttempt,
 } from './tbank-access.service';
+import { isTbankErrorCode, TbankErrorCode } from './tbank-error-code';
 import { TbankClient, type TbankInstrument } from './tbank.client';
 export { metadataKey } from './instrument-metadata.repository';
 export type { MetadataIdentity } from './instrument-metadata.repository';
@@ -131,7 +132,7 @@ export class InstrumentMetadataService {
                 if (
                   !identity.figi ||
                   (error instanceof Error &&
-                    error.message === 'INVALID_TBANK_TOKEN')
+                    isTbankErrorCode(error.message, TbankErrorCode.InvalidToken))
                 ) {
                   throw error;
                 }
@@ -191,11 +192,11 @@ export class InstrumentMetadataService {
             );
           }
         } catch (error) {
-          if (error instanceof Error && error.message === 'INVALID_TBANK_TOKEN') {
+          if (error instanceof Error && isTbankErrorCode(error.message, TbankErrorCode.InvalidToken)) {
             await this.access.rejectMembershipToken(attempt);
           } else {
             this.logger.event('warn', 'instrument-metadata.failed', {
-              code: 'TBANK_UNAVAILABLE',
+              code: TbankErrorCode.Unavailable,
             });
           }
         }
@@ -209,7 +210,7 @@ export class InstrumentMetadataService {
       }
     } catch {
       this.logger.event('error', 'instrument-metadata.persistence-failed', {
-        code: 'TBANK_UNAVAILABLE',
+        code: TbankErrorCode.Unavailable,
       });
       this.active.clear();
       this.producers.clear();