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

docs/protocols/common/user-points-chat-data-protocol.md

@@ -98,7 +98,7 @@ Protocol verification status:
 ### register_bonus_claims
 
 - PK: `id`
-- Core fields: `email_hash`, `user_email_snapshot`, `first_user_id_snapshot`, `balance_snapshot`, `grant_event_id`, `created_at`, `updated_at`
+- Core fields: `email_hash`, `user_email_snapshot`, `first_user_id_snapshot`, `balance_snapshot`, `grant_event_id`, `has_purchased_starter_pack`, `created_at`, `updated_at`
 - Constraints:
   - `email_hash` unique
   - `grant_event_id` unique
@@ -106,6 +106,7 @@ Protocol verification status:
   - `email_hash` must be HMAC-SHA256 over normalized email (`trim + lower`)
   - key source: backend config `points_policy.register_bonus_hmac_key`
   - `balance_snapshot` stores the latest pre-delete account balance for same-email re-registration recovery
+  - `has_purchased_starter_pack` tracks whether user has purchased the starter pack ($0.99/60 credits)
 
 #### points_ledger.metadata (schema_version=1)
 
@@ -206,3 +207,93 @@ Managed by `python -m core.runtime.cli sync-notifications [flags]`:
   - `--source-key <key>` — sync only the notification with the matching `source_key`
 
 Run after migrations on fresh environments or after adding new notification YAML definitions. Not included in `bootstrap` to keep bootstrap fast and free of unintended side effects.
+
+## Packages API
+
+### GET /api/v1/points/packages
+
+Returns available purchase packages for the current user's region, including starter pack eligibility.
+
+**Request:**
+- Auth: Required (JWT)
+- Headers: `Authorization: Bearer <token>`
+
+**Response:**
+```json
+{
+  "region": "US",
+  "currency": "USD",
+  "packages": [
+    {
+      "productCode": "new_user_pack_099_60",
+      "type": "starter",
+      "priceUsd": "0.99",
+      "credits": 60,
+      "badge": null,
+      "isStarter": true,
+      "starterEligible": true,
+      "sortOrder": 0
+    },
+    {
+      "productCode": "basic_pack_499_100",
+      "type": "regular",
+      "priceUsd": "4.99",
+      "credits": 100,
+      "badge": null,
+      "isStarter": false,
+      "starterEligible": false,
+      "sortOrder": 10
+    }
+  ]
+}
+```
+
+**Fields:**
+- `region`: ISO 3166-1 alpha-2 country code (e.g., "US", "CN")
+- `currency`: ISO 4217 currency code (e.g., "USD")
+- `packages`: List of available packages
+  - `productCode`: Unique product identifier
+  - `type`: "starter" (new user pack) or "regular"
+  - `priceUsd`: Price in USD (decimal string)
+  - `credits`: Number of credits
+  - `badge`: Optional badge text (e.g., "Popular")
+  - `isStarter`: Whether this is a starter pack
+  - `starterEligible`: Whether user is eligible to purchase starter pack
+  - `sortOrder`: Display order (ascending)
+
+**Business Logic:**
+1. Determine user's region from `profile.settings.preferences.country` (default: "US")
+2. Load package configuration from `backend/src/core/config/static/packages/{country}.yaml` (fallback to `default.yaml`)
+3. Check starter pack eligibility:
+   - If `register_bonus_claims.has_purchased_starter_pack = true`, exclude starter pack from response
+   - Otherwise, include starter pack with `starterEligible: true`
+
+**Configuration Files:**
+- Path: `backend/src/core/config/static/packages/`
+- Format: YAML
+- Example: `us.yaml`
+
+```yaml
+region: US
+currency: USD
+packages:
+  - product_code: new_user_pack_099_60
+    type: starter
+    price_usd: "0.99"
+    credits: 60
+    badge: null
+    sort_order: 0
+    enabled: true
+  - product_code: basic_pack_499_100
+    type: regular
+    price_usd: "4.99"
+    credits: 100
+    badge: null
+    sort_order: 10
+    enabled: true
+```
+
+**Country/Region Codes:**
+- Uses ISO 3166-1 alpha-2 standard
+- Default: `US` (United States)
+- Examples: `CN` (China), `TW` (Taiwan), `HK` (Hong Kong), `JP` (Japan)