Run background jobs on a pg-boss queue; add e2e tests, CI and deploy script

Timed jobs move from in-process timers to a job registry run by pg-boss:
once per schedule across processes, retries, run history, cron schedules
in the church timezone, and an admin Background jobs page with Run now.
Playwright end-to-end tests run against their own seeded database. A
Gitea Actions workflow runs backend tests, frontend checks and the e2e
tests, and deploys v* tags with scripts/deploy.sh once secrets are set.
Also fixes the at-the-door check-in count for multi-day tickets.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/prisma/migrations/20261022150000_add_job_run_audit_action/migration.sql

@@ -0,0 +1,2 @@
+-- AlterEnum
+ALTER TYPE "AdminAuditAction" ADD VALUE 'job_run_manual';

backend/prisma/schema.prisma

@@ -554,6 +554,7 @@ enum AdminAuditAction {
   attendance_unmarked
   certificate_issued
   certificate_revoked
+  job_run_manual
 }
 
 // Append-only audit trail for admin/supervisor-initiated actions with money or