fix(seo): escape inline JSON-LD, per-release byArtist, soft-404 + env-gated noindex

Escape </>& in JSON-LD body to kill script-breakout; byArtist now uses the release artist; detail-page not-found branches emit noindex; default robots gated to Production via a PersistentState SeoEnvironment bridge.

DeepDrftPublic.Client/Startup.cs

@@ -50,6 +50,11 @@ public static class Startup
         // image, social links). Singleton: stateless config, identical in the server-prerender and WASM
         // passes (this method runs in both), which is what makes SeoHead's double-render output identical.
         services.AddSingleton(new SeoOptions());
+
+        // Environment-gated robots bridge. Scoped + [PersistentState] like DarkModeSettings: the server
+        // seeds IsProduction during prerender and it rounds to the WASM pass, so SeoHead resolves the same
+        // default robots in both render passes (non-production → noindex,nofollow, keeping beta uncrawled).
+        services.AddScoped<SeoEnvironment>();
     }
 
     public static void ConfigureApiHttpClient(IServiceCollection services, string baseAddress)