feat: implement storeGroupValue and getGroupValue with unified locator

- API Refactoring: Extracted GroupValueLocator input type to unify parameters for storeGroupValue (mutation) and getGroupValue (query).

- Data Retrieval: Implemented getGroupValue query to allow direct retrieval of JSON values stored in host groups via Zabbix Trapper items.

- Enhanced Logic: Added ZabbixGetGroupValueRequest to fetch latest history values for group-associated items.

- Improved Verification: Updated the regression suite (REG-STORE) to include a full 'Store-Update-Retrieve' verification cycle.

- Documentation:

    - Updated docs/howtos/cookbook.md recipes to use the new locator structure and getGroupValue for verification.

    - Updated sample query files (docs/queries/) with corrected variables and verification queries.

- Tests:

    - Added unit and integration tests for getGroupValue.

    - Updated existing tests to match the refactored storeGroupValue schema.

- Verification: Verified 100% pass rate for all 16 regression steps and all unit/integration tests.

.junie/guidelines.md

@@ -35,6 +35,7 @@ The [Roadmap](../roadmap.md) is to be considered as outlook giving constraints o
 
 ## Best Practices & Standards
 - **ESM & Imports**: The project uses ECMAScript Modules (ESM). Always use the `.js` extension when importing local files (e.g. `import { Config } from "../common_utils.js";`), even though the source files are `.ts`.
+- **Zabbix API Requests**: Always use dedicated request classes (extending `ZabbixRequest`) for interacting with the Zabbix API. Avoid using `zabbixAPI.requestByPath` directly in business logic or data sources, as request classes provide better type safety and parameter optimization.
 - **Configuration**: Always use the `Config` class to access environment variables. Avoid direct `process.env` calls.
 - **Type Safety**: Leverage types generated via `npx graphql-codegen --config codegen.ts` (or `npm run codegen` for watch mode) for resolvers and data handling to ensure consistency with the schema.
 - **Import Optimization**: