Initial commit: import from sinmb79/Gov-chat-bot

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/providers/llm.py

@@ -0,0 +1,28 @@
+from abc import ABC, abstractmethod
+from typing import Optional
+
+
+class LLMProvider(ABC):
+    @abstractmethod
+    async def generate(
+        self,
+        system_prompt: str,
+        user_message: str,
+        context_chunks: list,
+        max_tokens: int = 512,
+    ) -> Optional[str]:
+        """실패 시 None 반환. 예외 raise 금지."""
+        ...
+
+
+class NullLLMProvider(LLMProvider):
+    """LLM_PROVIDER=none 기본값"""
+
+    async def generate(
+        self,
+        system_prompt: str = "",
+        user_message: str = "",
+        context_chunks: list = None,
+        max_tokens: int = 512,
+    ) -> None:
+        return None