feat: implement comprehensive testing framework and regression suite

- Established a centralized test specification in docs/tests.md that defines test categories, cases, and a coverage checklist to ensure consistent quality and maintainability across the project.

- Implemented RegressionTestExecutor for managing automated regression tests on a live Zabbix system.

- Updated GraphQL schema and resolvers with a generic runAllRegressionTests mutation.

- Enhanced MCP integration with new operation files and detailed documentation for AI-driven automation.

- Updated README.md and How-To guides (Cookbook, Maintenance, MCP) to reflect the new testing framework and MCP capabilities.

- Verified all changes with a full Jest suite (74 tests) and live end-to-end smoketests.

src/api/resolvers.ts

@@ -27,6 +27,7 @@ import {
 import {HostImporter} from "../execution/host_importer.js";
 import {HostDeleter} from "../execution/host_deleter.js";
 import {SmoketestExecutor} from "../execution/smoketest_executor.js";
+import {RegressionTestExecutor} from "../execution/regression_test_executor.js";
 import {TemplateImporter} from "../execution/template_importer.js";
 import {TemplateDeleter} from "../execution/template_deleter.js";
 import {HostValueExporter} from "../execution/host_exporter.js";
@@ -276,6 +277,12 @@ export function createResolvers(): Resolvers {
                 cookie
             }: any) => {
                 return SmoketestExecutor.runSmoketest(args.hostName, args.templateName, args.groupName, zabbixAuthToken, cookie)
+            },
+            runAllRegressionTests: async (_parent: any, args: any, {
+                zabbixAuthToken,
+                cookie
+            }: any) => {
+                return RegressionTestExecutor.runAllRegressionTests(args.hostName, args.groupName, zabbixAuthToken, cookie)
             }
         },