Add Zigbee support and new render widgets

[PHKenny]

This pull request introduces support for Zigbee and ConfIoT-related configurations by updating enums and adding new fields to the Model class. It also enhances the Model data structure with visual representation capabilities, including icon and widget metadata. These changes improve the flexibility and expressiveness of device models, particularly for frontend rendering and protocol support.

Support for Zigbee and ConfIoT:

• Added zigbee to the OperationMode enum and its serialization map, enabling explicit Zigbee protocol support. [1] [2]
• Updated the changelog to document the new Zigbee and ConfIoT features.

Enhancements to the Model class:

• Added new fields to Model: icon (with LayrzIcon? type and converter) for visual representation, and widget (with RenderWidget enum) to indicate the rendering widget for device type visualization. Updated constructors, copy methods, and equality/hash implementations accordingly. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
• Added necessary imports and part files to support new icon and widget features. [1] [2]

Minor improvements:

• Minor formatting change in ConfigSource enum for consistency.

[github-actions]

📋 Changelog Summary

This PR includes the following changes:

✨ Features

• Add support for Zigbee and new render widgets (0b7bba8 by @PHKenny)

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[github-actions]

📊 Test Coverage Report

🎯 Dart/Flutter

Metric	Value
Coverage	11.0%
Lines covered	14917 / 449
Lines missing	-14468

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