Hide tabs based on user authorization levels

[WilliamBZA]

Summary

Gates the ServicePulse UI on the set of ServiceControl API routes the signed-in user is actually allowed to call (the my/routes manifest). Navigation items and Configuration sub-tabs the user cannot reach are hidden; action buttons they cannot use are disabled with an explanatory tooltip (not hidden), so the UI stays discoverable.

Gating is fail-open: it only applies once authorization is enabled, the user is authenticated, and the manifest has loaded. In every other state the full UI is shown, so an unreachable or slow ServiceControl never locks a user out.

This PR consolidates the work previously split across #3041 and #3044. It supersedes the earlier permission-string gating model, which was introduced and then removed on this branch in favour of the route-based approach.

How it works

• Route registry (composables/apiRoutes.ts): maps each gated UI capability to the ServiceControl HTTP route it represents. This is the single point of coupling to ServiceControl's route surface; the UI gates on routes it already calls, never on internal permission names.
• Structural matching (composables/routeMatching.ts): normalizes a (method, path) pair into a comparison key with route parameters collapsed to {}, so matching couples to method plus path structure and survives server-side parameter renames.
• Manifest store (stores/AllowedRoutesStore.ts): fetches my/routes from the Primary and Monitoring instances, merges them, and keeps a per-store in-flight guard so concurrent callers share one request. Per-instance fail-open: a failed or non-array response is ignored rather than fataled.
• Gating primitive (composables/useAllowedRoutes.ts): exposes canCall and canAnyCall. Resource-owning stores call these and surface capability getters; templates bind to those getters.
• PermissionGate wrapper (components/PermissionGate.vue): reusable component that disables a slotted action and shows a tooltip with the reason when the user lacks the route, instead of removing the control.

What is gated

• Navigation menu (PageHeader.vue) and Configuration sub-tabs
  (ConfigurationView.vue): hidden when no backing route is allowed.
• Action buttons, disabled with tooltip: failed messages, deleted messages and message groups, custom-check dismiss, heartbeat endpoint instances, redirects, health-check notifications (manage and test), edit and retry, and monitored endpoint deletion.
• Resource-owning stores expose capability getters: HealthChecksStore, HeartbeatInstancesStore, MessageStore, MonitoringEndpointDetailsStore, RedirectsStore, ThroughputStore.
• A new User Permissions configuration page (UserPermissions.vue) renders the capabilities derived from the user's allowed routes.

Design decisions

• Fail-open everywhere: uncertainty (auth disabled, not yet authenticated, manifest not loaded) shows the UI rather than hiding it.
• Gate on routes the UI already calls, decoupling the frontend from ServiceControl's internal permission model.
• Structural, parameter-insensitive route keys so the contract is method plus path shape, not exact parameter names.
• The manifest is stored as a Map (not a Set) so a future per-route resource scope can be carried per entry.
• The startup fetch surfaces a 403 denial reason so an explicitly forbidden user gets a clear message.

Backend dependency

Requires ServiceControl to serve the my/routes allowed-route manifest on the
Primary instance, and the equivalent on the Monitoring instance.

Reviewer Checklist

• Components are broken down into sensible and maintainable sub-components.
• Styles are scoped to the component using it. If multiple components need to share CSS, then a .css file is created containing the shared CSS and imported into component scoped style sections.
• Naming is consistent with existing code, and adequately describes the component or function being introduced
• Only functions utilizing Vue state or lifecycle hooks are named as composables (i.e. starting with 'use');
• No module-level state is being introduced. If so, request the PR author to move the state to the corresponding Pinia store.

[ramonsmits]

Added some improvement on:

• #3036