Add OpenTelemetry and Prometheus metrics infrastructure

examples/otel-collector-config.yaml

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+receivers:
+  otlp:
+    protocols:
+      grpc:
+        endpoint: 0.0.0.0:4317
+      http:
+        endpoint: 0.0.0.0:4318
+
+processors:
+  batch:
+    timeout: 10s
+    send_batch_size: 1024
+  
+  # Add resource attributes
+  resource:
+    attributes:
+      - key: service.environment
+        value: "development"
+        action: insert
+
+exporters:
+  # Prometheus exporter for scraping
+  prometheus:
+    endpoint: "0.0.0.0:8889"
+    namespace: "gerbil"
+    send_timestamps: true
+    metric_expiration: 5m
+    resource_to_telemetry_conversion:
+      enabled: true
+
+  # Prometheus remote write (optional)
+  prometheusremotewrite:
+    endpoint: "http://prometheus:9090/api/v1/write"
+    tls:
+      insecure: true
+  
+  # Debug exporter for debugging
+  debug:
+    verbosity: normal
+
+service:
+  pipelines:
+    metrics:
+      receivers: [otlp]
+      processors: [batch, resource]
+      exporters: [prometheus, prometheusremotewrite, debug]

examples/prometheus.yml

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+global:
+  scrape_interval: 15s
+  evaluation_interval: 15s
+  external_labels:
+    cluster: 'gerbil-dev'
+
+scrape_configs:
+  # Scrape Gerbil's /metrics endpoint directly
+  - job_name: 'gerbil'
+    static_configs:
+      - targets: ['gerbil:3003']
+        labels:
+          service: 'gerbil'
+          environment: 'development'
+
+  # Scrape OpenTelemetry Collector metrics
+  - job_name: 'otel-collector'
+    static_configs:
+      - targets: ['otel-collector:8888']
+        labels:
+          service: 'otel-collector'
+      - targets: ['otel-collector:8889']
+        labels:
+          service: 'otel-collector-prometheus-exporter'