feat: add template and template group management via GraphQL

- Implemented GraphQL endpoints for importing, querying, and deleting Zabbix templates and template groups. - Added support for full template data import, including items, preprocessing steps, tags, and linked templates. - Implemented dependent item support by deferred creation logic in the template importer. - Added ability to query templates and template groups with name pattern filtering (supporting Zabbix wildcards). - Implemented batch deletion for templates and template groups by ID or name pattern. - Improved error reporting by including detailed Zabbix API error data in GraphQL responses. - Added comprehensive unit and integration tests covering all new functionality. - Provided GraphQL sample queries and mutations in the 'docs' directory for all new endpoints.

docs/sample_delete_template_groups_mutation.graphql

@@ -0,0 +1,30 @@
+### Mutation
+Use this mutation to delete template groups by their numeric IDs or by a name pattern.
+
+```graphql
+mutation DeleteTemplateGroups($groupids: [Int!], $name_pattern: String) {
+  deleteTemplateGroups(groupids: $groupids, name_pattern: $name_pattern) {
+    id
+    message
+    error {
+      message
+      code
+      data
+    }
+  }
+}
+```
+
+### Variables (by ID)
+```json
+{
+  "groupids": [201]
+}
+```
+
+### Variables (by name pattern)
+```json
+{
+  "name_pattern": "Templates/Roadwork/%"
+}
+```