feat(admin): enrich admin panel fields; add user index constraint and customer service

- admin controller: add updatedAt to interview/resume selects; add orderCount,
  todayOrders, totalRevenue to overview
- admin.vue: enrich all tabs with more fields
  - overview: order cards (count, revenue)
  - users: wxOpenid, email, createdAt, interviewCount, vipExpireAt, role badge
  - interviews: user email, updatedAt, summary preview
  - orders: title, type, channel, paidAt, wxTransactionId, refund info
  - resumes: user email, updatedAt
  - share: sharer phone, shareCode, isActive, visitorId(IP), creditedAt
  - admins: email, createdAt
- user.schema: add unique indexes on phone/wxOpenid/email; pre-save hook
  requiring at least one contact method
- user/about: add WeChat contact button (open-type=contact) for customer service

backend/src/modules/user/user.schema.ts

@@ -5,10 +5,10 @@ export type UserDocument = User & Document
 
 @Schema({ timestamps: true })
 export class User {
-  @Prop({ sparse: true })
+  @Prop({ unique: true, sparse: true })
   phone?: string
 
-  @Prop({ sparse: true })
+  @Prop({ unique: true, sparse: true })
   wxOpenid?: string
 
   @Prop({ default: '' })
@@ -60,11 +60,18 @@ export class User {
   @Prop({ default: false })
   isSystemAdmin: boolean
 
-  @Prop({ sparse: true })
+  @Prop({ unique: true, sparse: true })
   email?: string
 
   @Prop({ default: '', select: false })
   password?: string
 }
 
-export const UserSchema = SchemaFactory.createForClass(User)
+export const UserSchema = SchemaFactory.createForClass(User)
+
+UserSchema.pre('save', function (next) {
+  if (!this.phone && !this.wxOpenid && !this.email) {
+    return next(new Error('用户必须至少有一个联系方式（手机号/微信/邮箱）'))
+  }
+  next()
+})