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/json_utils.py

@@ -0,0 +1,19 @@
+import json
+import re
+
+from app.core.exceptions import LLMParseError
+
+
+def extract_json(text: str) -> any:
+    """Parse JSON from LLM response, stripping Markdown code fences if present."""
+    text = text.strip()
+
+    # Strip ```json ... ``` or ``` ... ``` fences
+    fence_match = re.search(r"```(?:json)?\s*([\s\S]+?)\s*```", text)
+    if fence_match:
+        text = fence_match.group(1).strip()
+
+    try:
+        return json.loads(text)
+    except json.JSONDecodeError as e:
+        raise LLMParseError(f"大模型返回非合法 JSON: {e}") from e