llm_comfyui: orphan llm.prompt.template records cause KeyError on uninstall

## Bug

The model `llm.prompt.template` was removed during the consolidation into `llm.prompt` (via `llm_assistant`), but `llm_comfyui/data/llm_prompt_data.xml` still contains two `` blocks referencing it:

- `llm_prompt_template_comfyui_workflow` (line 29)
- `llm_prompt_template_comfyui_character_gen_v1` (line 205)

## Impact

Attempting to uninstall the `llm` module (or any llm_* module) via the Odoo Apps UI fails with:

```
KeyError: 'llm.prompt.template'
```

Traceback path: `ir_module.py > button_immediate_uninstall > registry.new > load_modules > module_uninstall > _module_data_uninstall > env[model_name] > KeyError`

## Root cause

The two orphan records contain ComfyUI workflow JSON templates (~3280 lines of JSON node definitions). These records used fields (`prompt_id`, `role`, `sequence`, `content`) that belonged to the now-removed `llm.prompt.template` model.

## Discussion: workflow template data migration

The removed records contained valuable ComfyUI workflow definitions. If this data should be preserved, a migration path is needed. However, `llm.prompt` does not have the equivalent fields that `llm.prompt.template` had.

Options:
1. Accept the removal (data was already non-functional)
2. Recreate a compatible model or add fields to `llm.prompt`
3. Store the workflow JSON in an existing text field on `llm.prompt`

We would appreciate guidance from maintainers on the preferred approach.

## Environment

- Odoo 16.0 CE
- odoo-llm branch 16.0 (latest)
- Tested on Windows 10 Pro, PostgreSQL 12.4