feat(event-bingo): add VictoriaMetrics metrics scraping

- Add name: http to backend-service port (required for VMServiceScrape)
- Add VMServiceScrape for /metrics endpoint (30s interval)
- Register vm-service-scrape.yaml in kustomization

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: soohyunme

services/event-bingo/base/backend-service.yaml

@@ -7,5 +7,6 @@ spec:
     app: event-bingo
     component: backend
   ports:
-    - port: 8000
+    - name: http
+      port: 8000
       targetPort: 8000

services/event-bingo/base/kustomization.yaml

@@ -5,3 +5,4 @@ resources:
   - frontend-service.yaml
   - backend-deployment.yaml
   - backend-service.yaml
+  - vm-service-scrape.yaml

services/event-bingo/base/vm-service-scrape.yaml

@@ -0,0 +1,13 @@
+apiVersion: operator.victoriametrics.com/v1beta1
+kind: VMServiceScrape
+metadata:
+  name: event-bingo-backend
+spec:
+  selector:
+    matchLabels:
+      app: event-bingo
+      component: backend
+  endpoints:
+    - port: http
+      path: /metrics
+      interval: 30s