Fix #142: Any method to add my trained model to advanced tools?

[JiwaniZakir]

Closes #142

Model option lists for the advanced tools panel were previously hardcoded in advanced_tools_api.py; this moves them into src/constant.json under web_ui.sequence_model_options and web_ui.structure_model_options, so operators can register custom trained models by editing config rather than source code.

In src/constant.json, two new keys are added to the web_ui object with the existing defaults as their values. In src/web_v2/advanced_tools_api.py, the advanced_tools_meta function (lines ~714–715) now calls web_ui.get("sequence_model_options", [...]) and web_ui.get("structure_model_options", [...]) instead of returning inline literals, preserving backward compatibility when the keys are absent.

tests/test_advanced_tools_meta.py is added with three unit tests: test_default_model_options_when_not_in_constant confirms the fallback literals are returned when the keys are missing, test_custom_model_options_from_constant confirms a custom entry like "MyTrainedModel" is surfaced when set in config, and test_constant_json_has_model_option_keys reads the actual src/constant.json on disk and asserts both keys are present and are lists.

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This PR was created with AI assistance (Claude). The changes were reviewed by quality gates and a critic model before submission.