Add shellgen core and backends modules

app/shellgen/backends/__init__.py

@@ -0,0 +1,12 @@
+"""LLM backends for command generation."""
+
+from .base import LLMBackend
+from .ollama import OllamaBackend
+from .factory import BackendFactory
+
+try:
+    from .llama_cpp import LlamaCppBackend
+except ImportError:
+    LlamaCppBackend = None
+
+__all__ = ["LLMBackend", "OllamaBackend", "LlamaCppBackend", "BackendFactory"]