Fix comprehensive lint and type errors across codebase

- Replace explicit 'any' types with 'unknown' or specific types
- Fix Jest DOM test setup with proper type definitions
- Resolve NODE_ENV assignment errors using Object.defineProperty
- Fix React Hook dependency warnings with useCallback patterns
- Remove unused variables and add appropriate ESLint disables
- Update documentation with groups feature information
- Ensure all tests pass with proper TypeScript compliance

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/__tests__/useToast.test.ts

@@ -178,7 +178,7 @@ describe('useToast', () => {
   it('returns unique IDs for each toast', () => {
     const { result } = renderHook(() => useToast());
     
-    let id1: string, id2: string;
+    let id1: string = '', id2: string = '';
     
     act(() => {
       // Mock different random values for unique IDs