feat: nKode React + TypeScript SPA scaffold

- React + Vite + Tailwind CSS v4 + React Router
- Keypad component: 10-digit pad with dot indicators, keyboard support, haptic feel
- Auth pages: Login (email → keypad), Signup (email → method → keypad/key)
- Home page: session info, practice keypad
- Admin dashboard: placeholder stats + user management
- Developer dashboard: OIDC client registration UI placeholder
- WASM client wrapper: lazy loads from /wasm/, falls back to mock client
- TypeScript type declarations for nkode-client-wasm package
- Dark mode with system preference detection
- Auth state management with localStorage persistence + auto-expiry
- Code splitting: lazy-loaded route pages (~236KB main bundle)
- Inter font, clean indigo/slate design system

src/types/nkode-client-wasm.d.ts

@@ -0,0 +1,19 @@
+/**
+ * Type stub for the nKode WASM package.
+ * Will be replaced by real types when the package is linked via `bun link`.
+ */
+declare module 'nkode-client-wasm' {
+  export class NKodeClient {
+    constructor(base_url: string);
+    loginCode(email: string, passcode_bytes: Uint8Array): Promise<any>;
+    loginKey(email: string, secret_key_hex: string): Promise<any>;
+    registerCode(email: string, passcode_bytes: Uint8Array): Promise<void>;
+    registerKey(email: string, secret_key_hex: string): Promise<void>;
+    static generateSecretKey(): string;
+    free(): void;
+  }
+
+  export function init(): void;
+
+  export default function __wbg_init(module_or_path?: any): Promise<any>;
+}