Fix missing Google login button in managed environments

The Tuist server Helm chart now reads Google OAuth client credentials from a 1Password vault via External Secrets Operator, so the ‘Log in with Google’ button appears in managed environments that previously lacked it. A new server.google.managedSecrets value toggles the feature; when enabled, the chart renders an ExternalSecret and injects TUIST_GOOGLE_OAUTH_CLIENT_ID and TUIST_GOOGLE_OAUTH_CLIENT_SECRET into the server deployment. Self-hosted deployments that do not use Google OAuth keep the default false and are unaffected.