Initial cluster config: NixOS flake + k3s + 5 node definitions

- Multi-host flake.nix (3x N97 x86_64 + 2x RPi4 aarch64)
- Shared modules: k3s-cluster, tailscale, meos-gateway
- Node configs: n97-1 (control plane), n97-2/n97-3 (Ollama workers), rpi4-1/rpi4-2 (ARM workers)
- K8s manifests: Forgejo, Postgres (CNPG), Umami, OpenBrain, MeOS Dashboard, MCP servers
- Bootstrap and DB migration scripts
- Migration plan doc (7-day phased rollout)

apps/openbrain/deployment.yaml

@@ -0,0 +1,59 @@
+# OpenBrain MCP — deployed to ARM worker (rpi4-1)
+---
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: openbrain
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: openbrain
+  namespace: openbrain
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: openbrain
+  template:
+    metadata:
+      labels:
+        app: openbrain
+    spec:
+      nodeSelector:
+        kubernetes.io/arch: arm64
+      tolerations:
+        - key: "arm64"
+          operator: "Exists"
+          effect: "NoSchedule"
+      containers:
+        - name: openbrain
+          image: node:22-slim
+          command: ["node", "/app/index.js"]
+          workingDir: /app
+          ports:
+            - containerPort: 3000
+          env:
+            - name: NODE_ENV
+              value: production
+            - name: PORT
+              value: "3000"
+          resources:
+            requests:
+              memory: "128Mi"
+              cpu: "100m"
+            limits:
+              memory: "256Mi"
+              cpu: "250m"
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: openbrain
+  namespace: openbrain
+spec:
+  ports:
+    - port: 3000
+      targetPort: 3000
+  selector:
+    app: openbrain