feat: gallery + generic blueprint viewer, add Grid blueprint

Refactor the List-specific screen into a data-driven, reusable viewer:
- generic Blueprint type + shared LoadState machine + registry
- vue-router: / (gallery) and /b/:slug (illustration)
- BlueprintViewer renders any blueprint; specimens stay bespoke
- add Grid blueprint (6 functions incl. Position) + GridSpecimen

src/main.ts

@@ -1,5 +1,6 @@
 import { createApp } from "vue"
 import "./style.css"
 import App from "./App.vue"
+import { router } from "./router"
 
-createApp(App).mount("#app")
+createApp(App).use(router).mount("#app")