fix(loki): deploy Promtail as separate HelmChart

Loki chart v6.x removed Promtail as a subchart — the promtail: section
in loki values.yaml was silently ignored, so no log collection agent
was running (causing "No options found" in Grafana label browser).

Add Promtail 6.16.6 as its own HelmChart alongside Loki and move the
Promtail config into a dedicated promtail-values.yaml.

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

Author: soohyunme

infrastructure/base/monitoring/loki/kustomization.yaml

@@ -10,3 +10,9 @@ helmCharts:
     releaseName: loki
     namespace: monitoring
     valuesFile: values.yaml
+  - name: promtail
+    repo: https://grafana.github.io/helm-charts
+    version: 6.16.6
+    releaseName: promtail
+    namespace: monitoring
+    valuesFile: promtail-values.yaml

infrastructure/base/monitoring/loki/promtail-values.yaml

@@ -0,0 +1,28 @@
+config:
+  clients:
+    - url: http://loki:3100/loki/api/v1/push
+  scrape_configs:
+    - job_name: kubernetes-pods
+      kubernetes_sd_configs:
+        - role: pod
+      relabel_configs:
+        - source_labels: [__meta_kubernetes_pod_name]
+          action: replace
+          target_label: pod
+        - source_labels: [__meta_kubernetes_namespace]
+          action: replace
+          target_label: namespace
+        - source_labels: [__meta_kubernetes_pod_label_app]
+          action: replace
+          target_label: app
+        - source_labels: [__meta_kubernetes_pod_container_name]
+          action: replace
+          target_label: container
+
+resources:
+  limits:
+    cpu: 100m
+    memory: 128Mi
+  requests:
+    cpu: 50m
+    memory: 64Mi

infrastructure/base/monitoring/loki/values.yaml

@@ -68,34 +68,3 @@ loki:
           prefix: loki_index_
           period: 24h
 
-# Promtail - log collection agent
-promtail:
-  enabled: true
-  config:
-    clients:
-      - url: http://loki:3100/loki/api/v1/push
-    scrape_configs:
-      - job_name: kubernetes-pods
-        kubernetes_sd_configs:
-          - role: pod
-        relabel_configs:
-          - source_labels: [__meta_kubernetes_pod_name]
-            action: replace
-            target_label: pod
-          - source_labels: [__meta_kubernetes_namespace]
-            action: replace
-            target_label: namespace
-          - source_labels: [__meta_kubernetes_pod_label_app]
-            action: replace
-            target_label: app
-          - source_labels: [__meta_kubernetes_pod_container_name]
-            action: replace
-            target_label: container
-
-  resources:
-    limits:
-      cpu: 100m
-      memory: 128Mi
-    requests:
-      cpu: 50m
-      memory: 64Mi