## Why

The console already calls platform metrics and server config read APIs, but those routes are not implemented. Operators see empty/error states or local sample config even when real server, job, and run endpoint data exists. This change closes the read-only observability gap before write and execution work builds on it.

## What Changes

- Add backend contracts and routes for platform resource usage, per-server metrics, and server config reads.
- Enforce existing role-scoped server access for server config and server metrics.
- Return bounded, safe metadata without host paths, raw credentials, run sockets, or AI keys.
- Update HomePage and ServerDetailPage to prefer API data and keep any local samples as explicit dev/demo fallback only.
- Add tests and browser walkthrough coverage for 首页 and server detail config views.

## Capabilities

### New Capabilities

- `platform-observability-and-config-read`: API-backed platform/server metrics and safe server config read workflows.

### Modified Capabilities

- `platform-web-console-shell`: Removes production reliance on local observability/config samples for existing console pages.

## Impact

- Affects `platform/` domain, DTO, validators, service, API handlers, route docs, and tests.
- Affects `platform_web/` API types/client usage, HomePage, ServerDetailPage, tests, and browser walkthrough.
- Does not add config writes, file dispatch, log tail transport, external metrics backends, billing, cloud host sales, raw host paths, raw credentials, or direct run access.