fix(backend): extract shared indexer state id

backend/src/lib/indexer-state.ts

@@ -0,0 +1 @@
+export const INDEXER_STATE_ID = 'singleton';

backend/src/routes/health.routes.ts

@@ -1,5 +1,6 @@
 import { Router, type Request, type Response } from 'express';
 import { prisma } from '../lib/prisma.js';
+import { INDEXER_STATE_ID } from '../lib/indexer-state.js';
 
 const router = Router();
 
@@ -62,7 +63,7 @@ router.get('/', async (_req: Request, res: Response) => {
 
   let indexerLag = -1;
   try {
-    const state = await prisma.indexerState.findUnique({ where: { id: 'singleton' } });
+    const state = await prisma.indexerState.findUnique({ where: { id: INDEXER_STATE_ID } });
     if (state) {
       const now = Math.floor(Date.now() / 1000);
       const updatedAt = Math.floor(state.updatedAt.getTime() / 1000);

backend/src/routes/v1/admin.routes.ts

@@ -8,6 +8,7 @@ import {
 } from '../../services/indexerService.js';
 
 import { prisma } from '../../lib/prisma.js';
+import { INDEXER_STATE_ID } from '../../lib/indexer-state.js';
 import { sseService } from '../../services/sse.service.js';
 import { cache } from '../../lib/redis.js';
 import logger from '../../logger.js';
@@ -56,7 +57,7 @@ async function buildAdminMetrics() {
       where: { isActive: false, events: { some: { eventType: 'COMPLETED' } } },
     }),
     prisma.streamEvent.count({ where: { createdAt: { gte: since24h } } }),
-    prisma.indexerState.findUnique({ where: { id: 'singleton' } }),
+    prisma.indexerState.findUnique({ where: { id: INDEXER_STATE_ID } }),
     prisma.streamEvent.findMany({
       where: { eventType: 'FEE_COLLECTED' },
       select: { amount: true, metadata: true },

backend/src/services/indexerService.ts

@@ -1,9 +1,8 @@
 import { prisma } from '../lib/prisma.js';
+import { INDEXER_STATE_ID } from '../lib/indexer-state.js';
 import { sorobanEventWorker } from '../workers/soroban-event-worker.js';
 import logger from '../logger.js';
 
-const INDEXER_STATE_ID = 'singleton';
-
 export interface IndexerStatus {
   lastLedger: number;
   lastCursor: string | null;

backend/src/workers/soroban-event-worker.ts

@@ -1,12 +1,11 @@
 import { rpc, xdr, StrKey } from '@stellar/stellar-sdk';
 import { prisma } from '../lib/prisma.js';
+import { INDEXER_STATE_ID } from '../lib/indexer-state.js';
 import { sseService } from '../services/sse.service.js';
 import logger from '../logger.js';
 
 // ─── Config ──────────────────────────────────────────────────────────────────
 
-const INDEXER_STATE_ID = 'singleton';
-
 // ─── XDR Decoding Helpers ────────────────────────────────────────────────────
 
 /** Decode an ScVal symbol to a string. */