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

tests/conftest.py

@@ -0,0 +1,39 @@
+import pytest
+from unittest.mock import AsyncMock, MagicMock
+from fastapi.testclient import TestClient
+
+from app.clients.llm.base import LLMClient
+from app.clients.storage.base import StorageClient
+from app.core.dependencies import get_llm_client, get_storage_client
+
+
+@pytest.fixture
+def mock_llm() -> LLMClient:
+    client = MagicMock(spec=LLMClient)
+    client.chat = AsyncMock(return_value='[]')
+    client.chat_vision = AsyncMock(return_value='[]')
+    return client
+
+
+@pytest.fixture
+def mock_storage() -> StorageClient:
+    client = MagicMock(spec=StorageClient)
+    client.download_bytes = AsyncMock(return_value=b"")
+    client.upload_bytes = AsyncMock(return_value=None)
+    client.get_presigned_url = AsyncMock(return_value="http://example.com/presigned")
+    client.get_object_size = AsyncMock(return_value=10 * 1024 * 1024)  # 10 MB default
+    return client
+
+
+@pytest.fixture
+def test_app(mock_llm, mock_storage):
+    from app.main import app
+    app.dependency_overrides[get_llm_client] = lambda: mock_llm
+    app.dependency_overrides[get_storage_client] = lambda: mock_storage
+    yield app
+    app.dependency_overrides.clear()
+
+
+@pytest.fixture
+def client(test_app):
+    return TestClient(test_app)