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.

src/lib/claudeSyntaxTheme.ts

@@ -124,7 +124,7 @@ export const getClaudeSyntaxTheme = (theme: ThemeMode): any => {
       overflow: 'auto',
     },
     ':not(pre) > code[class*="language-"]': {
-      background: theme === 'light' || theme === 'white' 
+      background: theme === 'light' 
         ? 'rgba(139, 92, 246, 0.1)' 
         : 'rgba(139, 92, 246, 0.1)',
       padding: '0.1em 0.3em',