perf(webapp,database): index the newest-task-version lookup

Schedule validation seeks (projectId, slug) and then sorts every matching
row by createdAt to return one. A project gains a row per task per deploy,
so the sort grows with project age. Index the sort key so Postgres scans
backward and stops at the first row, and select only the field the check
reads.

Author: ericallam

.server-changes/faster-schedule-validation-lookup.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: improvement
+---
+
+Creating or updating a schedule, and deploying a project with declarative schedules, is faster in long-lived projects with many deploys.

apps/webapp/app/v3/services/checkSchedule.server.ts

@@ -45,6 +45,9 @@ export class CheckScheduleService extends BaseService {
         slug: schedule.taskIdentifier,
         projectId: projectId,
       },
+      select: {
+        triggerSource: true,
+      },
       orderBy: {
         createdAt: "desc",
       },

internal-packages/database/prisma/migrations/20260806100000_add_background_worker_task_project_id_slug_created_at_index/migration.sql

@@ -0,0 +1 @@
+CREATE INDEX CONCURRENTLY IF NOT EXISTS "BackgroundWorkerTask_projectId_slug_createdAt_idx" ON "public"."BackgroundWorkerTask"("projectId", "slug", "createdAt");

internal-packages/database/prisma/schema.prisma

@@ -752,6 +752,7 @@ model BackgroundWorkerTask {
   @@unique([workerId, slug])
   // Quick lookup of task identifiers
   @@index([projectId, slug])
+  @@index([projectId, slug, createdAt])
   @@index([runtimeEnvironmentId, projectId])
   @@index([runtimeEnvironmentId, slug, triggerSource])
 }