feat: 新人初始礼包购买追踪功能

- 数据库：添加 has_purchased_starter_pack 字段到 register_bonus_claims
- 后端：创建静态配置管理套餐信息，支持按国家/地区区分
- 后端：新增 GET /api/v1/points/packages API 返回可用套餐
- 后端：创建 utils/paths.py 统一路径管理
- 前端：动态获取套餐信息，移除硬编码
- 前端：添加 ProductCode 枚举约束，前后端类型安全
- 配置：Profile 默认国家改为 US（ISO 3166-1 alpha-2）
- 文档：更新协议文档说明新 API 和字段

backend/src/v1/points/repository.py

@@ -10,6 +10,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from models.agent_chat_message import AgentChatMessage
 from models.points_audit_ledger import PointsAuditLedger
 from models.points_ledger import PointsLedger
+from models.profile import Profile
 from models.register_bonus_claims import RegisterBonusClaims
 from models.user_points import UserPoints
 from schemas.domain.points import (
@@ -189,3 +190,22 @@ class PointsRepository:
         claim.balance_snapshot = int(balance_snapshot)
         await self._session.flush()
         return True
+
+    async def has_purchased_starter_pack(
+        self,
+        *,
+        email_hash: str,
+    ) -> bool:
+        claim = await self.get_register_bonus_claim(email_hash=email_hash)
+        if claim is None:
+            return False
+        return bool(claim.has_purchased_starter_pack)
+
+    async def get_profile_settings(
+        self,
+        *,
+        user_id: UUID,
+    ) -> dict[str, object] | None:
+        stmt = select(Profile.settings).where(Profile.id == user_id).limit(1)
+        row = (await self._session.execute(stmt)).scalar_one_or_none()
+        return row