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/utils/__tests__/configUtils.test.ts

@@ -57,7 +57,7 @@ describe("configUtils", () => {
         ...DEFAULT_INSPECTOR_CONFIG,
         MCP_PROXY_AUTH_TOKEN: {
           ...DEFAULT_INSPECTOR_CONFIG.MCP_PROXY_AUTH_TOKEN,
-          value: null as any,
+          value: null as unknown as string,
         },
       };
 
@@ -69,4 +69,4 @@ describe("configUtils", () => {
       });
     });
   });
-});
+});