feat(infra): set 90-day retention for monitoring services (#3402)

### Description

Loki, Tempo, Prometheus의 데이터 보관 기간(retention)을 90일로 설정합니다.

**변경 사항:**
| 서비스 | 이전 | 이후 |
|--------|------|------|
| Loki | 무제한 | 2160h (90일) |
| Tempo | 24h | 2160h (90일) |
| Prometheus | 10d | 90d |

**예상 스토리지 사용량 (Stage 기준):**
- Loki: ~10.5 GB
- Tempo: ~110 MB
- Prometheus: ~3 GB

### Additional context

closes TAS-2542

현재 PVC 용량(50-100Gi)으로 충분히 수용 가능합니다.

---

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and follow the [Commit
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- [x] Provide a description in this PR that addresses **what** the PR is
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- [ ] Ideally, include relevant tests that fail without this PR but pass
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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: manamana32321

infra/k8s/monitoring/loki/values.yaml

@@ -6,6 +6,10 @@ loki:
   auth_enabled: false
   commonConfig:
     replication_factor: 1
+  limits_config:
+    retention_period: 2160h # 90 days
+  compactor:
+    retention_enabled: true
   ring:
     kvstore:
       store: inmemory

infra/k8s/monitoring/prometheus/values-production.yaml

@@ -2,6 +2,8 @@ grafana:
   enabled: false
 
 prometheus:
+  prometheusSpec:
+    retention: 90d
   ingress:
     enabled: true
     hosts:

infra/k8s/monitoring/prometheus/values-stage.yaml

@@ -2,6 +2,8 @@ grafana:
   enabled: false
 
 prometheus:
+  prometheusSpec:
+    retention: 90d
   ingress:
     enabled: true
     hosts:

infra/k8s/monitoring/tempo/values.yaml

@@ -5,6 +5,9 @@ traces:
 
 tempo:
   structuredConfig:
+    compactor:
+      compaction:
+        block_retention: 2160h # 90 days
     ingester:
       lifecycler:
         ring: