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

requirements.txt

@@ -0,0 +1,16 @@
+fastapi>=0.111.0
+uvicorn[standard]>=0.29.0
+pydantic>=2.7.0
+zhipuai>=2.1.0
+boto3>=1.34.0
+pdfplumber>=0.11.0
+python-docx>=1.1.0
+opencv-python-headless>=4.9.0
+numpy>=1.26.0
+httpx>=0.27.0
+python-dotenv>=1.0.0
+pyyaml>=6.0.0
+
+# Testing
+pytest>=8.0.0
+pytest-asyncio>=0.23.0