baseline: Clover 独立仓库首次基线提交

将 Clover 从上层产品包旧仓库中独立出来,建立专属版本控制。
当前状态=纵切片端到端已打通(登录→选品→出文出图→审核→下载包),
M1文案质量去套路化已验收。此提交作为后续按核销清单逐条修复的基线。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/core/response.py

@@ -0,0 +1,63 @@
+"""
+app/core/response.py — 统一响应包络
+成功：{ "code": 0, "data": {...} }
+失败：{ "code": <错误码>, "message": "用户可读信息" }
+HTTP 状态码与业务 code 分离（契约§0）。
+"""
+
+from typing import Any
+
+from fastapi import HTTPException
+from fastapi.responses import JSONResponse
+
+from app.constants.enums import ErrorCode
+
+
+def ok(data: Any = None) -> dict:
+    """标准成功响应。"""
+    return {"code": ErrorCode.SUCCESS, "data": data}
+
+
+def err(code: int, message: str) -> dict:
+    """标准失败响应体（不含 HTTP 状态，由调用方决定）。"""
+    return {"code": code, "message": message}
+
+
+def paginate(items: list, total: int, page: int, page_size: int) -> dict:
+    """分页数据包装。"""
+    return {
+        "items": items,
+        "total": total,
+        "page": page,
+        "page_size": page_size,
+    }
+
+
+# ── 常用异常 ──────────────────────────────────────────────
+class CloverHTTPException(HTTPException):
+    """携带业务 code 的 HTTP 异常，供全局 handler 格式化。"""
+
+    def __init__(self, http_status: int, code: int, message: str):
+        super().__init__(status_code=http_status, detail=message)
+        self.biz_code = code
+        self.biz_message = message
+
+
+def raise_not_found(message: str = "资源不存在") -> None:
+    raise CloverHTTPException(404, ErrorCode.NOT_FOUND, message)
+
+
+def raise_forbidden(message: str = "无权限访问") -> None:
+    raise CloverHTTPException(403, ErrorCode.FORBIDDEN, message)
+
+
+def raise_unauthorized(message: str = "未认证或 Token 失效") -> None:
+    raise CloverHTTPException(401, ErrorCode.UNAUTHORIZED, message)
+
+
+def raise_business(message: str) -> None:
+    raise CloverHTTPException(422, ErrorCode.BUSINESS_ERROR, message)
+
+
+def raise_state_invalid(message: str = "状态机非法流转") -> None:
+    raise CloverHTTPException(409, ErrorCode.STATE_INVALID, message)