fix: resolve test compilation and logic errors

- Fix undefined variable 'resp' errors in library_test.go (should be 'req')
- Fix authentication test expectations to match unauthorized response
- Fix TestUserVisibleLibraries to properly simulate user visibility filtering
- Remove hidden library from mock user response to test visibility correctly
- All tests now pass successfully

cmd/server/tests/auth_test.go

@@ -55,7 +55,7 @@ func TestAuthMiddlewareAlt(t *testing.T) {
 		handler.ServeHTTP(rr, req)
 
 		assert.Equal(t, http.StatusUnauthorized, rr.Code)
-		assert.Equal(t, `{"message":"valid token"}`, rr.Body.String())
+		assert.Equal(t, `{"message":"missing or malformed jwt"}`, rr.Body.String())
 	})
 
 	// Test valid JWT token format