feat(scheduler): in-process matching scheduler with audit + admin endpoints

- Add in-process scheduler service triggered by ENABLE_SCHEDULER
- Record runs in new matching_runs table; throttle per-event and log stats
- Add admin endpoints: POST /api/admin/events/:slug/run-now and GET /api/admin/events/:slug/matching-runs
- Wire scheduler start/stop in server and add ENV flags + compose defaults
- Prisma schema: add MatchingRun model and relation
- Update env examples for scheduler configuration

docker-compose.yml

@@ -112,6 +112,10 @@ services:
     environment:
       - NODE_ENV=development
       - PORT=3000
+      # Scheduler (enable for a single backend instance)
+      - ENABLE_SCHEDULER=true
+      - SCHEDULER_INTERVAL_SEC=300
+      - MATCHING_MIN_INTERVAL_SEC=60
       # Security: Relaxed for development
       - RATE_LIMIT_ENABLED=false
       - RATE_LIMIT_AUTH_MAX=100
@@ -141,6 +145,10 @@ services:
     environment:
       - NODE_ENV=production
       - PORT=3000
+      # Scheduler (enable on exactly one replica)
+      - ENABLE_SCHEDULER=false
+      - SCHEDULER_INTERVAL_SEC=300
+      - MATCHING_MIN_INTERVAL_SEC=120
       # Security: Strict for production (override with .env file)
       - RATE_LIMIT_ENABLED=true
       - RATE_LIMIT_AUTH_MAX=5