feat: add a runtime diagnostics page

Adds GET /api/clouds/:cloud/diagnostics and a Diagnostics page in the
General nav. The report combines, in one call:

- runtime reachability, latency, version and edition from /_floci/health
- every service the runtime emulates, with the console pages backed by it
- per-console-service probes (the existing status check)
- EC2 instance containers from /_floci/diagnose
- console uptime, sign-in mode and active session count

Each source is optional, so a down runtime still yields a partial report.

packages/frontend/src/api/api.ts

@@ -13,6 +13,7 @@ export const apiEndpointKeys = {
     list: "clouds.list",
     services: "clouds.services.list",
     status: "clouds.status.get",
+    diagnostics: "clouds.diagnostics.get",
     serviceStatus: "clouds.services.status.get",
     schema: "clouds.services.schema.get",
     dependencies: "clouds.services.dependencies.get",
@@ -323,6 +324,13 @@ export const endpointRegistry: EndpointRegistry = new Map([
       method: "GET",
     },
   ],
+  [
+    apiEndpointKeys.clouds.diagnostics,
+    {
+      path: "/clouds/:cloud/diagnostics",
+      method: "GET",
+    },
+  ],
   [
     apiEndpointKeys.clouds.serviceStatus,
     {