initial project scaffold

Rust workspace with nomina-core (rename engine) and nomina-app (Tauri v2 shell).
React/TypeScript frontend with tabbed rule panels, virtual-scrolled file list,
and Zustand state management. All 9 rule types implemented with 25 passing tests.

crates/nomina-app/build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    tauri_build::build()
+}