feat(server): Support self-hosted Kura endpoints

Resolves N/A

Adds self-hosted Kura endpoint support for on-premise Tuist deployments. The server can now read Kura endpoints from runtime configuration, the Tuist Helm chart can render those endpoints into the server pod, and the Kura Helm chart is included in Helm validation and release publishing.

The self-hosting docs now split the old installation page into a Control plane page, remove the legacy cache-node pages from the sidebar, point existing cache-node users to the deprecated source docs, and add a Kura page that explains why Kura is decentralized, how to deploy it with or without Kubernetes, and which runtime variables operators can configure.

How to test locally

• git diff --check origin/main...HEAD
• helm lint kura/ops/helm/kura
• helm template kura kura/ops/helm/kura > /tmp/kura-rendered.yaml && wc -l /tmp/kura-rendered.yaml
• helm package kura/ops/helm/kura --destination /tmp
• helm lint infra/helm/tuist --set 'server.kuraEndpointUrls[0]=http://kura:4000'
• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/release.yml"); YAML.load_file(".github/workflows/helm.yml"); puts "ok"'
• mix test test/tuist/environment_test.exs test/tuist/accounts_test.exs test/tuist/docs/redirects_test.exs (fails during test database setup with Postgrex.Error because relation users does not exist)