fix: replace require() imports with ES modules in tests

- Replaced all require() imports with proper ES module imports
- Fixed ESLint @typescript-eslint/no-require-imports errors
- Removed unused variable mockGetMCPProxyAddress
- Added proper TypeScript types instead of 'any'
- All tests passing and linting clean

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

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

client/src/App.tsx

@@ -347,9 +347,10 @@ const App = () => {
 
   useEffect(() => {
     const headers: HeadersInit = {};
-    const proxyAuthToken = getMCPProxyAuthToken(config);
+    const { token: proxyAuthToken, header: proxyAuthTokenHeader } =
+      getMCPProxyAuthToken(config);
     if (proxyAuthToken) {
-      headers["Authorization"] = `Bearer ${proxyAuthToken}`;
+      headers[proxyAuthTokenHeader] = `Bearer ${proxyAuthToken}`;
     }
 
     fetch(`${getMCPProxyAddress(config)}/config`, { headers })