API v3alpha: StatusService #5477

Parent: #5450

Delivered status.v3alpha.StatusService.GetStatus through #5317 and #5377. Returns version/build information, configuration, start time, and cluster status.

Supports Connect HTTP GET with Cache-Control: no-store, Connect/gRPC-Web under the route-prefixed /api/, and native gRPC at the server root. Health and reflection remain available alongside API v2.

Further hardening: #5478. This issue remains complete.