feat: add GroundValueChecker and WeatherSensorDevice with public API integration

This commit introduces two new device types, GroundValueChecker and WeatherSensorDevice, which leverage public APIs (BORIS NRW and Open-Meteo) for real-time data collection. It also includes several API enhancements and fixes to support these new integrations.

Detailed changes:
- **New Device Types**:
  - Added GroundValueChecker schema and integration with BORIS NRW WMS via Zabbix Script items.
  - Added WeatherSensorDevice schema and integration with Open-Meteo via Zabbix HTTP Agent items.
- **API Enhancements**:
  - Added error field to ZabbixItem for item-level error reporting.
  - Updated CreateTemplateItem mutation input to support params (for Script items) and timeout.
  - Registered missing scalar resolvers: JSONObject, DateTime, and Time.
- **Performance & Reliability**:
  - Implemented batch fetching for item preprocessing in both host and template queries to reduce Zabbix API calls and ensure data visibility.
  - Updated template_importer.ts to correctly handle Script item parameters.
- **Documentation**:
  - Consolidated public API device recipes in docs/howtos/cookbook.md.
  - Added guidance on analyzing data update frequency and setting reasonable update intervals (e.g., 1h for weather, 1d for ground values).
- **Testing**:
  - Added new regression test REG-ITEM-META to verify item metadata (units, description, error, preprocessing) and JSONObject scalar support.
  - Enhanced RegressionTestExecutor with more detailed host-item relationship verification.

schema/extensions/ground_value_checker.graphql

@@ -0,0 +1,46 @@
+"""
+GroundValueChecker represents a device that retrieves ground values
+from public APIs (e.g. BORIS NRW) using Zabbix HTTP agent items.
+"""
+type GroundValueChecker implements Host & Device {
+    """Internal Zabbix ID of the device."""
+    hostid: ID!
+    """
+    Per convention a uuid is used as hostname to identify devices if they do not have a unique hostname.
+    """
+    host: String!
+    """Classification of the device."""
+    deviceType: String
+    """List of host groups this device belongs to."""
+    hostgroups: [HostGroup!]
+    """Visible name of the device."""
+    name: String
+    """Device configuration tags."""
+    tags: DeviceConfig
+    """Host inventory data."""
+    inventory: Inventory
+    """List of monitored items for this host."""
+    items: [ZabbixItem!]
+    """State of the ground value checker device."""
+    state: GroundValueState
+}
+
+"""
+Represents the state of a ground value checker device.
+"""
+type GroundValueState implements DeviceState {
+    """Operational data (telemetry)."""
+    operational: OperationalDeviceData
+    """Current business values (ground data)."""
+    current: GroundValues
+}
+
+"""
+Aggregated ground information retrieved from the API.
+"""
+type GroundValues {
+    """
+    Average ground value (in €/m²). Extracted from the BORIS NRW GeoJSON response.
+    """
+    averageValue: Float
+}