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/main.py

@@ -0,0 +1,46 @@
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+
+from app.core.exceptions import (
+    AIServiceError,
+    ai_service_exception_handler,
+    unhandled_exception_handler,
+)
+from app.core.logging import RequestLoggingMiddleware, get_logger
+
+logger = get_logger(__name__)
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    logger.info("startup", extra={"message": "AI service starting"})
+    yield
+    logger.info("shutdown", extra={"message": "AI service stopping"})
+
+
+app = FastAPI(
+    title="Label AI Service",
+    description="知识图谱标注平台 AI 计算服务",
+    version="1.0.0",
+    lifespan=lifespan,
+)
+
+app.add_middleware(RequestLoggingMiddleware)
+app.add_exception_handler(AIServiceError, ai_service_exception_handler)
+app.add_exception_handler(Exception, unhandled_exception_handler)
+
+
+@app.get("/health", tags=["Health"])
+async def health():
+    return {"status": "ok"}
+
+
+# Routers registered after implementation (imported lazily to avoid circular deps)
+from app.routers import text, image, video, qa, finetune  # noqa: E402
+
+app.include_router(text.router, prefix="/api/v1")
+app.include_router(image.router, prefix="/api/v1")
+app.include_router(video.router, prefix="/api/v1")
+app.include_router(qa.router, prefix="/api/v1")
+app.include_router(finetune.router, prefix="/api/v1")