fix: resolve LRU cache test failures and TypeScript linting errors

- Fix module resolution issues in LRU cache tests by using proper vi.mock() with importActual
- Fix mock call count expectations by using valid API keys instead of empty strings
- Add explicit types to test objects to resolve TypeScript linting errors
- Change logger mock types to 'any' to avoid complex type issues
- Add vi.clearAllMocks() for proper test isolation

All tests now pass and TypeScript linting succeeds without errors.

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

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

tests/unit/flexible-instance-security-advanced.test.ts

@@ -21,7 +21,7 @@ vi.mock('../../src/utils/logger');
 describe('Advanced Security and Error Handling Tests', () => {
   let mockN8nApiClient: Mock;
   let mockGetN8nApiConfigFromContext: Mock;
-  let mockLogger: Mock;
+  let mockLogger: any; // Logger mock has complex type
 
   beforeEach(() => {
     vi.resetAllMocks();