feat(devgen): add Ollama provider and host configuration

Add support for the Ollama provider in the AI generation pipeline and expose a configurable host address.

New Features:
- Introduce `ollama` as a selectable provider.
- Add `ollama_host` configuration option with default `http://localhost:11434`.

Enhancements:
- Extend provider list in error message to include Ollama.

devgen/utils.py

@@ -229,6 +229,7 @@ def load_config() -> Dict[str, Any]:
             "api_key": "",
             "emoji": True,
             "max_groups": 5,
+            "ollama_host": "http://localhost:11434",
         }
         try:
             with config_path.open("w", encoding="utf-8") as f: