feat: Phase 0 — monorepo 骨架 + 全表迁移 + FastAPI/Next 骨架 + CI

- uv(workspace) + pnpm monorepo；docker-compose(pg+api+web)
- SQLAlchemy 16 MVP 表 + Alembic 初版迁移(无漂移，users stub)
- FastAPI 骨架：统一错误信封(带 request_id) + structlog + /jobs/:id + OpenAPI
- Next.js 骨架：纸感主题 token + OpenAPI→TS 客户端代码生成(gen:api)
- CI(ruff/mypy/pytest + pg service + alembic 漂移校验)
- 四份设计规格(PRODUCT/UX/ARCHITECTURE/DEV_PLAN) + CLAUDE.md

packages/shared/ww_shared/errors.py

@@ -0,0 +1,44 @@
+"""统一错误码与领域异常（ARCH §7.1）。"""
+
+from __future__ import annotations
+
+from enum import StrEnum
+
+
+class ErrorCode(StrEnum):
+    NOT_FOUND = "NOT_FOUND"
+    VALIDATION = "VALIDATION"
+    CONFLICT_UNRESOLVED = "CONFLICT_UNRESOLVED"  # 未决冲突禁验收
+    LLM_UNAVAILABLE = "LLM_UNAVAILABLE"  # 回退耗尽
+    RATE_LIMITED = "RATE_LIMITED"
+    INTERNAL = "INTERNAL"
+
+
+# 错误码 -> HTTP 状态
+HTTP_STATUS: dict[ErrorCode, int] = {
+    ErrorCode.NOT_FOUND: 404,
+    ErrorCode.VALIDATION: 422,
+    ErrorCode.CONFLICT_UNRESOLVED: 409,
+    ErrorCode.LLM_UNAVAILABLE: 503,
+    ErrorCode.RATE_LIMITED: 429,
+    ErrorCode.INTERNAL: 500,
+}
+
+
+class AppError(Exception):
+    """领域异常：在边界处映射为统一错误信封。"""
+
+    def __init__(
+        self,
+        code: ErrorCode,
+        message: str,
+        details: dict[str, object] | None = None,
+    ) -> None:
+        super().__init__(message)
+        self.code = code
+        self.message = message
+        self.details = details or {}
+
+    @property
+    def http_status(self) -> int:
+        return HTTP_STATUS.get(self.code, 500)