…o Global apps

In Blazor WASM/Auto Global interactivity projects, all interactive pages and
layout components live in the .Client project, not the server project. The
Identity scaffolder was always generating Account pages into the server project,
so they were never reachable and no register/login UI appeared.

Fix: detect WASM/Auto Global projects by checking for the absence of
Components/Layout/MainLayout.razor in the server project directory (same
heuristic as PR #3764). When detected, redirect the scaffolded Account files
to the .Client sibling project and update all namespaces accordingly.

Changes:
- BlazorIdentityModel: add RootNamespace property for path resolution
- BlazorIdentityGenerator (VS path): detect WASM/Auto Global via project
  references, set BaseOutputPath/BlazorIdentityNamespace/BlazorLayoutNamespace/
  RootNamespace to the client project; use RootNamespace in ExecuteTemplates
- IdentityModel (CLI): add IdentityProjectName for client project path resolution
- ValidateIdentityStep (CLI): detect WASM/Auto Global via sibling .Client folder,
  set BaseOutputPath/IdentityNamespace/IdentityLayoutNamespace/IdentityProjectName
- BlazorIdentityHelper (CLI): use IdentityProjectName in StringUtil.ToPath call
- BlazorIdentityScaffolderBuilderExtensions (CLI): use IdentityModel.BaseOutputPath
  for static file placement instead of always using the server project directory

Does not repro on Blazor Server Global or per-page/component projects because
MainLayout.razor exists in the server project for those configurations.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>