REVERT(otel): remove metrics collection, keep logs/traces only

- Revert to simpler architecture where Prometheus scrapes metrics directly via ServiceMonitors
- OTel Collector only handles logs (filelog) and traces (otlp)
- Remove Target Allocator and metrics-related config
- This reduces complexity and resource usage for home cluster

opentelemetry-collector/manifests/kustomization.yaml

@@ -3,5 +3,4 @@ kind: Kustomization
 
 resources:
   - rbac.yaml
-  - collector-logs.yaml
-  - collector-metrics.yaml
+  - collector.yaml