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

setup/pi-monitoring/ARCHITECTURE.md

@@ -0,0 +1,33 @@
+# Pi Monitoring Architecture
+
+## Goal
+
+Use Raspberry Pi as lightweight control/observability plane for Docker hosts in this project.
+
+## Topology
+
+```text
+                 +------------------------------+
+                 | Raspberry Pi (ops node)      |
+                 | Portainer + Grafana          |
+                 | Prometheus + Uptime Kuma     |
+                 +---------------+--------------+
+                                 |
+                     Portainer Agent (9001)
+                +----------------+----------------+
+                |                                 |
+      +---------v---------+             +---------v---------+
+      | Unraid Docker host|             | Fedora Docker host|
+      | Gitea primary     |             | Gitea backup      |
+      +-------------------+             +-------------------+
+```
+
+## Data paths
+
+- Pi local metrics: `node-exporter` + `cadvisor` -> Prometheus -> Grafana
+- Remote host control: Portainer -> remote `portainer_agent`
+- Availability checks: Uptime Kuma -> HTTP/TCP checks for Gitea and other services
+
+## Persistence
+
+All service data is stored under `OPS_ROOT` (default `/srv/ops`) on SSD.