fix(build): resolve TypeScript errors and add missing dependencies

- Add missing zustand dependency to package.json
- Fix unused variable errors in ToolWidgets.tsx
- Remove invalid 'white' theme comparison in claudeSyntaxTheme.ts
- Add proper TypeScript types to stores using StateCreator pattern
- Add null checks and type casting in Settings.tsx filter operations
- Add onChange handler to Switch component to suppress React warning
- Add 'check' script for TypeScript validation

These changes ensure the TypeScript build passes without errors.

package.json

@@ -8,7 +8,8 @@
     "dev": "vite",
     "build": "tsc && vite build",
     "preview": "vite preview",
-    "tauri": "tauri"
+    "tauri": "tauri",
+    "check": "tsc --noEmit && cd src-tauri && cargo check"
   },
   "dependencies": {
     "@hookform/resolvers": "^3.9.1",