feat(analytics): replace custom pipeline with Matomo

Removes the hand-rolled analytics endpoint and SQLite event table in favour
of Matomo — a self-hosted, full-featured analytics platform.

k8s:
- Deploy MariaDB 11 + Bitnami Matomo 5 in the solitaire namespace
- Route analytics.aleshym.co ingress to the Matomo service
- Remove Datasette sidecar and its BasicAuth middleware/secret
- Remove the analytics port from the solitaire-server Service

Rust:
- Replace AnalyticsClient (custom HTTP endpoint) with MatomoClient (Matomo
  HTTP Tracking API bulk endpoint); maps game events to Matomo categories
- Add matomo_url + matomo_site_id fields to Settings (serde default → None/1)
- Privacy toggle in Settings now activates when matomo_url is set (not tied
  to SyncBackend::SolitaireServer)
- Remove POST /api/analytics route from solitaire_server

Web:
- Add Matomo JS tracking snippet to game.html (/play page)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

deploy/mariadb-service.yaml

@@ -0,0 +1,13 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: mariadb
+  namespace: solitaire
+spec:
+  selector:
+    app: mariadb
+  ports:
+    - name: mysql
+      port: 3306
+      targetPort: 3306
+  clusterIP: None