feat: web dashboard for live device data

Small companion service that receives SNEK callbacks, decodes Sens'it
Discovery payloads for all 6 modes (Standby, Temperature, Light, Door,
Vibration, Magnet), stores in SQLite, and serves a responsive dashboard.

Backend (Python Flask):
- POST /webhook: receive SNEK callback
- GET /api/devices, /api/messages, /api/decode
- GET /events: Server-Sent Events for live push
- SQLite persistence at /data/messages.db

Frontend:
- Tailwind CSS via CDN, Chart.js for temp/humidity graph
- Live updates via SSE
- Device cards with icons per mode
- Message log with human-readable summaries

Deploy:
- Separate deployment (snek-dashboard) with own PVC
- LoadBalancer on 192.168.1.213:80
- SNEK callback URL: http://snek-dashboard.snek.svc.cluster.local/webhook

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

deploy/dashboard.yaml

@@ -0,0 +1,75 @@
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: dashboard-data
+  namespace: snek
+spec:
+  accessModes:
+    - ReadWriteOnce
+  storageClassName: local-path
+  resources:
+    requests:
+      storage: 1Gi
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: snek-dashboard
+  namespace: snek
+spec:
+  replicas: 1
+  strategy:
+    type: Recreate
+  selector:
+    matchLabels:
+      app: snek-dashboard
+  template:
+    metadata:
+      labels:
+        app: snek-dashboard
+    spec:
+      containers:
+        - name: dashboard
+          image: 192.168.1.100:30500/snek-dashboard:latest
+          imagePullPolicy: Always
+          ports:
+            - containerPort: 3000
+              name: http
+          env:
+            - name: DB_PATH
+              value: /data/messages.db
+          volumeMounts:
+            - name: data
+              mountPath: /data
+          readinessProbe:
+            httpGet:
+              path: /healthz
+              port: 3000
+            initialDelaySeconds: 5
+            periodSeconds: 10
+          resources:
+            requests:
+              cpu: 50m
+              memory: 64Mi
+            limits:
+              cpu: 500m
+              memory: 256Mi
+      volumes:
+        - name: data
+          persistentVolumeClaim:
+            claimName: dashboard-data
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: snek-dashboard
+  namespace: snek
+spec:
+  type: LoadBalancer
+  loadBalancerIP: 192.168.1.213
+  selector:
+    app: snek-dashboard
+  ports:
+    - name: http
+      port: 80
+      targetPort: 3000