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

docker-compose.yml

@@ -0,0 +1,37 @@
+version: "3.9"
+
+services:
+  ai-service:
+    build: .
+    ports:
+      - "8000:8000"
+    env_file:
+      - .env
+    depends_on:
+      rustfs:
+        condition: service_healthy
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
+      interval: 30s
+      timeout: 5s
+      retries: 3
+      start_period: 10s
+
+  rustfs:
+    image: rustfs/rustfs:latest
+    ports:
+      - "9000:9000"
+    environment:
+      RUSTFS_ACCESS_KEY: ${STORAGE_ACCESS_KEY}
+      RUSTFS_SECRET_KEY: ${STORAGE_SECRET_KEY}
+    volumes:
+      - rustfs_data:/data
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:9000/health"]
+      interval: 10s
+      timeout: 3s
+      retries: 5
+      start_period: 5s
+
+volumes:
+  rustfs_data: