chore: add tests for schema and API config mocking

- Added unit tests for schema loader, mocking Config variables and resolvers.
- Added unit tests for Zabbix API configuration, verifying constants derived from Config.
- Mocked relevant modules and filesystem behaviors to enable isolated testing.
- Optimized imports on all files and include this within a new .junie/guidelines.md file

src/test/logger_config.test.ts

@@ -0,0 +1,18 @@
+// Import after mocking Config
+import {logger, Loglevel} from "../logging/logger.js";
+
+// Mocking Config
+jest.mock("../common_utils.js", () => ({
+    Config: {
+        LOG_LEVELS: "ERROR,INFO"
+    }
+}));
+
+describe("Logger Config Mocking", () => {
+    test("logger levels are initialized from Config", () => {
+        expect(logger.levels).toBeDefined();
+        expect(logger.levels?.has(Loglevel.ERROR)).toBe(true);
+        expect(logger.levels?.has(Loglevel.INFO)).toBe(true);
+        expect(logger.levels?.has(Loglevel.DEBUG)).toBe(false);
+    });
+});