Embed Elsa Studio Blazor WASM in the same host

- Elsa.Studio.Wasm project (net9.0): WASM shell with Login/Dashboard/Workflows modules,
  reads its backend URL from a JS-injected window.getClientConfig() so the same build
  can point at any origin without a rebuild.
- Elsa.CustomServer:
    - references Elsa.Studio.Wasm as a project so `dotnet publish` emits its wwwroot/
    - UseBlazorFrameworkFiles + MapFallbackToPage('/_Host') serve the WASM app + SPA routes
    - Pages/_Host.cshtml renders the Studio shell and injects apiUrl at request time
- Bumped Elsa server packages to 3.5.3, Studio packages to 3.7.0 (Studio release train
  moved ahead of server; 3.7 Studio is compatible with 3.5 server API)
- Dockerfile: SDK/runtime 9.0, restores both csprojs before copying sources

Dockerfile

@@ -1,11 +1,12 @@
 # Elsa Custom Server — Docker image
 # Multi-stage build so the final image only carries the ASP.NET runtime.
 
-FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
+FROM mcr.microsoft.com/dotnet/sdk:9.0 AS build
 WORKDIR /source
 
 # Restore first for better layer caching.
 COPY src/Elsa.CustomServer/Elsa.CustomServer.csproj src/Elsa.CustomServer/
+COPY src/Elsa.Studio.Wasm/Elsa.Studio.Wasm.csproj src/Elsa.Studio.Wasm/
 RUN dotnet restore src/Elsa.CustomServer/Elsa.CustomServer.csproj
 
 # Then copy the rest and publish.
@@ -13,7 +14,7 @@ COPY src/ src/
 RUN dotnet publish src/Elsa.CustomServer/Elsa.CustomServer.csproj \
     -c Release -o /app/publish --no-restore /p:UseAppHost=false
 
-FROM mcr.microsoft.com/dotnet/aspnet:8.0 AS runtime
+FROM mcr.microsoft.com/dotnet/aspnet:9.0 AS runtime
 WORKDIR /app
 COPY --from=build /app/publish ./