新增小程序后端代码，包括数据库、路由、服务层等。

小程序前后端打通，包括登录、注册、绑定设备、查询绑定信息，修改小朋友名称等功能。

banban-mini/src/services/binding.ts

@@ -0,0 +1,105 @@
+import { request } from './api'
+
+export interface Binding {
+  device_id: string
+  child_id: number
+  status: number
+  bound_at: string
+}
+
+export interface BindStartResponse {
+  bind_token: string
+  expires_at: string
+}
+
+export interface BindHistoryItem {
+  device_id: string
+  child_id: number
+  bound_at: string
+  unbound_at?: string
+}
+
+export interface BindHistoryResponse {
+  items: BindHistoryItem[]
+  total: number
+  next_cursor?: string
+}
+
+// 获取当前绑定信息
+export async function getCurrentBinding(): Promise<Binding | null> {
+  try {
+    return await request<Binding>('/bindings/current')
+  } catch (err: any) {
+    if (err.status === 404) {
+      return null
+    }
+    throw err
+  }
+}
+
+// 开始绑定设备
+export async function startBind(data: {
+  device_id: string
+  child_id: number
+}): Promise<BindStartResponse> {
+  return request<BindStartResponse>('/bindings/start', {
+    method: 'POST',
+    data,
+  })
+}
+
+// 确认绑定设备
+export async function confirmBind(data: {
+  bind_token: string
+  challenge_code: string
+}): Promise<{ device_id: string; child_id: number }> {
+  return request('/bindings/confirm', {
+    method: 'POST',
+    data,
+  })
+}
+
+// 获取设备绑定信息
+export async function getBinding(deviceId: string): Promise<Binding | null> {
+  // If no deviceId, get the first binding for this user
+  if (!deviceId) {
+    try {
+      // Try to get binding list - for now return null if no specific device
+      return null
+    } catch {
+      return null
+    }
+  }
+  return request<Binding>(`/bindings/${deviceId}`)
+}
+
+// 解绑设备
+export async function unbindDevice(deviceId: string): Promise<void> {
+  return request(`/bindings/${deviceId}`, {
+    method: 'DELETE',
+  })
+}
+
+// 直接绑定设备（手动输入设备码）
+export async function directBind(data: {
+  device_id: string
+  child_id: number
+}): Promise<{ device_id: string; child_id: number }> {
+  return request('/bindings/direct', {
+    method: 'POST',
+    data,
+  })
+}
+
+// 获取绑定历史
+export async function getBindHistory(
+  deviceId: string,
+  cursor?: string,
+  limit: number = 20
+): Promise<BindHistoryResponse> {
+  const params = new URLSearchParams()
+  if (cursor) params.append('cursor', cursor)
+  params.append('limit', String(limit))
+  
+  return request<BindHistoryResponse>(`/bindings/history/${deviceId}?${params.toString()}`)
+}