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>

types/jest-dom.d.ts

@@ -0,0 +1,10 @@
+// Jest DOM type definitions
+import '@testing-library/jest-dom';
+
+declare global {
+  namespace NodeJS {
+    interface ProcessEnv {
+      NODE_ENV: 'development' | 'production' | 'test';
+    }
+  }
+}