feat: add Pi monitoring stack with deployment scripts and architecture documentation

setup/pi-monitoring/prometheus/prometheus.yml

@@ -0,0 +1,24 @@
+global:
+  scrape_interval: 15s
+  evaluation_interval: 15s
+
+scrape_configs:
+  - job_name: prometheus
+    static_configs:
+      - targets: ["prometheus:9090"]
+
+  - job_name: pi-node
+    static_configs:
+      - targets: ["node-exporter:9100"]
+
+  - job_name: pi-cadvisor
+    static_configs:
+      - targets: ["cadvisor:8080"]
+
+  # Add Fedora/Unraid (or any remote host) targets in:
+  #   /srv/ops/prometheus/targets/external.yml
+  # A template is generated from external.yml.example by deploy_stack.sh.
+  - job_name: external-node-exporters
+    file_sd_configs:
+      - files:
+          - /etc/prometheus/targets/*.yml