feat(portal-shell): implement portal-shell with apollo-router integration

M8: portal-shell unified frontend shell (Modular Monolith + micro-kernel).

- Apollo Client -> apollo-router (port 4010, RSC prefetch)

- 5 layouts: classic/focus/split/triple/canvas

- Registry + PluginLoader (dynamic import ssr:false)

- 3-layer props merge, Zustand PluginStore

- 4 widgets: grades/notification-bell/user-menu/class-selector

- config-service: new pluginConfig GraphQL resolver

- apollo-router: CORS + header propagation for portal-shell

- docker-compose.yml: portal-shell service block

services/config-service/src/graphql/graphql.module.ts

@@ -20,6 +20,7 @@ import { ConfigModule } from "../config-config/config.module.js";
 import { PluginResolver } from "./resolvers/plugin.resolver.js";
 import { LayoutTemplateResolver } from "./resolvers/layout-template.resolver.js";
 import { UserLayoutResolver } from "./resolvers/user-layout.resolver.js";
+import { PluginConfigResolver } from "./resolvers/plugin-config.resolver.js";
 import { DataLoaderService } from "./dataloader.service.js";
 
 @Module({
@@ -50,6 +51,7 @@ import { DataLoaderService } from "./dataloader.service.js";
     PluginResolver,
     LayoutTemplateResolver,
     UserLayoutResolver,
+    PluginConfigResolver,
     DataLoaderService,
   ],
   exports: [DataLoaderService],