feat: 新增等级与奖章系统

- 后端: 新增 user_levels, exp_history, badge_definitions, user_badges, level_configs 表
- 后端: 新增 LevelService 和 BadgeService 服务
- 后端: 新增等级/奖章/签到/排行榜 API 端点
- 后端: 考试/练习/陪练完成时触发经验值和奖章检查
- 前端: 新增 LevelBadge, ExpProgress, BadgeCard, LevelUpDialog 组件
- 前端: 新增排行榜页面
- 前端: 成长路径页面集成真实等级数据
- 数据库: 包含迁移脚本和初始数据

frontend/src/api/level.ts

@@ -0,0 +1,182 @@
+/**
+ * 等级与奖章 API
+ */
+
+import request from '@/api/request'
+
+// 类型定义
+export interface LevelInfo {
+  user_id: number
+  level: number
+  exp: number
+  total_exp: number
+  title: string
+  color: string
+  login_streak: number
+  max_login_streak: number
+  last_checkin_at: string | null
+  next_level_exp: number
+  exp_to_next_level: number
+  is_max_level: boolean
+}
+
+export interface ExpHistoryItem {
+  id: number
+  exp_change: number
+  exp_type: string
+  description: string
+  level_before: number | null
+  level_after: number | null
+  created_at: string
+}
+
+export interface LeaderboardItem {
+  rank: number
+  user_id: number
+  username: string
+  full_name: string | null
+  avatar_url: string | null
+  level: number
+  title: string
+  color: string
+  total_exp: number
+  login_streak: number
+}
+
+export interface Badge {
+  id: number
+  code: string
+  name: string
+  description: string
+  icon: string
+  category: string
+  condition_type?: string
+  condition_value?: number
+  exp_reward: number
+  unlocked?: boolean
+  unlocked_at?: string | null
+}
+
+export interface CheckinResult {
+  success: boolean
+  message: string
+  exp_gained: number
+  base_exp?: number
+  bonus_exp?: number
+  login_streak: number
+  leveled_up?: boolean
+  new_level?: number | null
+  already_checked_in?: boolean
+  new_badges?: Badge[]
+}
+
+// API 函数
+
+/**
+ * 获取当前用户等级信息
+ */
+export function getMyLevel() {
+  return request.get<LevelInfo>('/level/me')
+}
+
+/**
+ * 获取指定用户等级信息
+ */
+export function getUserLevel(userId: number) {
+  return request.get<LevelInfo>(`/level/user/${userId}`)
+}
+
+/**
+ * 每日签到
+ */
+export function dailyCheckin() {
+  return request.post<CheckinResult>('/level/checkin')
+}
+
+/**
+ * 获取经验值历史
+ */
+export function getExpHistory(params?: {
+  limit?: number
+  offset?: number
+  exp_type?: string
+}) {
+  return request.get<{
+    items: ExpHistoryItem[]
+    total: number
+    limit: number
+    offset: number
+  }>('/level/exp-history', { params })
+}
+
+/**
+ * 获取等级排行榜
+ */
+export function getLeaderboard(params?: {
+  limit?: number
+  offset?: number
+}) {
+  return request.get<{
+    items: LeaderboardItem[]
+    total: number
+    limit: number
+    offset: number
+    my_rank: number
+    my_level_info: LevelInfo
+  }>('/level/leaderboard', { params })
+}
+
+/**
+ * 获取所有奖章定义
+ */
+export function getAllBadges() {
+  return request.get<Badge[]>('/level/badges/all')
+}
+
+/**
+ * 获取用户奖章（含解锁状态）
+ */
+export function getMyBadges() {
+  return request.get<{
+    badges: Badge[]
+    total: number
+    unlocked_count: number
+  }>('/level/badges/me')
+}
+
+/**
+ * 获取未通知的新奖章
+ */
+export function getUnnotifiedBadges() {
+  return request.get<Badge[]>('/level/badges/unnotified')
+}
+
+/**
+ * 标记奖章为已通知
+ */
+export function markBadgesNotified(badgeIds?: number[]) {
+  return request.post('/level/badges/mark-notified', badgeIds)
+}
+
+/**
+ * 手动检查并授予奖章
+ */
+export function checkAndAwardBadges() {
+  return request.post<{
+    new_badges: Badge[]
+    count: number
+  }>('/level/check-badges')
+}
+
+export default {
+  getMyLevel,
+  getUserLevel,
+  dailyCheckin,
+  getExpHistory,
+  getLeaderboard,
+  getAllBadges,
+  getMyBadges,
+  getUnnotifiedBadges,
+  markBadgesNotified,
+  checkAndAwardBadges
+}