fix: 修复后端代码违规并更新协议文档

- 修复 notifications 模块 datetime.now() 缺少时区问题
- 用 ApiProblemError 替换 BaseService 中的 HTTPException
- 更新协议文档：添加错误码、繁体字段、邀请相关协议
- 升级 Docker 镜像版本

docs/protocols/invite/invite-protocol.md

@@ -0,0 +1,49 @@
+# Invite Protocol (Frontend <-> Backend)
+
+This document defines the invite code contract for authenticated users.
+
+Protocol verification status:
+
+- Backend route source: `backend/src/v1/invite/router.py`
+- Backend service source: `backend/src/v1/invite/service.py`
+- Backend schema source: `backend/src/v1/invite/schemas.py`
+- Frontend mapping source: `apps/lib/features/settings/data/apis/invite_api.dart`
+
+## Compatibility strategy
+
+- Additive evolution only.
+- Existing response fields are stable and must remain backward-compatible.
+
+## Route
+
+### GET /api/v1/invite/me
+
+Get the current user's invite code information.
+
+**Authorization**: Requires authenticated session. User identity from JWT `sub`.
+
+**Response (200)**:
+
+```json
+{
+  "code": "ABC123XYZ",
+  "used_count": 5
+}
+```
+
+Field rules:
+
+- `code`: string, unique invite code assigned to the user
+- `used_count`: integer `>= 0`, number of times this code has been used
+
+## Error contract linkage
+
+- RFC7807 + extension `code`, optional `params`.
+- Shared registry: `docs/protocols/common/http-error-codes.md`.
+- Error codes for this feature:
+  - `INVITE_CODE_NOT_FOUND` (404): Invite code not found for current user
+
+## Data model linkage
+
+- Invite codes are stored in `invite_codes` table.
+- See `docs/protocols/common/user-points-chat-data-protocol.md` for `profiles.referred_by` field.