feat: Phase 1+2 — project setup and core infrastructure

- requirements.txt, config.yaml, .env, Dockerfile, docker-compose.yml
- app/core: config (YAML+env override), logging (JSON structured),
  exceptions (typed hierarchy), json_utils (Markdown fence stripping)
- app/clients: LLMClient ABC + ZhipuAIClient (run_in_executor),
  StorageClient ABC + RustFSClient (boto3 head_object for size check)
- app/main.py: FastAPI app with health endpoint and router registration
- app/core/dependencies.py: lru_cache singleton factories
- tests/conftest.py: mock_llm, mock_storage, test_app, client fixtures
- pytest.ini: asyncio_mode=auto
- 11 unit tests passing

app/core/dependencies.py

@@ -0,0 +1,23 @@
+from functools import lru_cache
+
+from app.clients.llm.base import LLMClient
+from app.clients.llm.zhipuai_client import ZhipuAIClient
+from app.clients.storage.base import StorageClient
+from app.clients.storage.rustfs_client import RustFSClient
+from app.core.config import get_config
+
+
+@lru_cache(maxsize=1)
+def get_llm_client() -> LLMClient:
+    cfg = get_config()
+    return ZhipuAIClient(api_key=cfg["zhipuai"]["api_key"])
+
+
+@lru_cache(maxsize=1)
+def get_storage_client() -> StorageClient:
+    cfg = get_config()
+    return RustFSClient(
+        endpoint=cfg["storage"]["endpoint"],
+        access_key=cfg["storage"]["access_key"],
+        secret_key=cfg["storage"]["secret_key"],
+    )