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/schemas.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+from typing import Literal
+
 from pydantic import BaseModel, ConfigDict, Field
 
 
@@ -11,3 +13,23 @@ class PointsBalanceResponse(BaseModel):
     available_balance: int = Field(alias="availableBalance", ge=0)
     run_cost: int = Field(alias="runCost", gt=0)
     can_run: bool = Field(alias="canRun")
+
+
+class PackageInfo(BaseModel):
+    model_config = ConfigDict(populate_by_name=True, serialize_by_alias=True)
+
+    product_code: str = Field(alias="productCode", min_length=1, max_length=128)
+    type: Literal["starter", "regular"]
+    price: float = Field(ge=0)
+    credits: int = Field(ge=1)
+    is_starter: bool = Field(alias="isStarter")
+    starter_eligible: bool = Field(alias="starterEligible")
+    sort_order: int = Field(alias="sortOrder", ge=0)
+
+
+class PackagesResponse(BaseModel):
+    model_config = ConfigDict(populate_by_name=True, serialize_by_alias=True)
+
+    region: str = Field(min_length=1, max_length=8)
+    currency: str = Field(min_length=1, max_length=8)
+    packages: list[PackageInfo]