refactor: 清理无用模块、修复前后端对齐、添加注册页面

- 删除后端 risk_exceptions 模块（API/Model/Schema/迁移/测试）
- 删除后端 metrics 模块（API/测试）
- 删除后端 ManualTask 模型和相关 Schema
- 修复搜索接口响应缺少 total 字段的问题
- 统一 Platform 枚举（前端去掉后端不支持的 weibo/wechat）
- 新增前端注册页面 /register，登录页添加注册链接

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/app/login/page.tsx

@@ -162,6 +162,14 @@ function LoginForm() {
           </button>
         </form>
 
+        {/* 注册链接 */}
+        <p className="text-center text-sm text-text-secondary">
+          还没有账号？{' '}
+          <Link href="/register" className="text-accent-indigo hover:underline font-medium">
+            立即注册
+          </Link>
+        </p>
+
         {/* Demo 登录 */}
         <div className="pt-6 border-t border-border-subtle">
           <p className="text-sm text-text-tertiary text-center mb-4">快速体验（Demo 账号）</p>

frontend/app/register/page.tsx

@@ -0,0 +1,233 @@
+'use client'
+
+import { useState } from 'react'
+import { useRouter } from 'next/navigation'
+import { useAuth } from '@/contexts/AuthContext'
+import { ShieldCheck, AlertCircle, ArrowLeft, Mail, Lock, User, Phone } from 'lucide-react'
+import Link from 'next/link'
+import type { UserRole } from '@/lib/api'
+
+const roleOptions: { value: UserRole; label: string; desc: string }[] = [
+  { value: 'brand', label: '品牌方', desc: '创建项目、管理代理商、配置审核规则' },
+  { value: 'agency', label: '代理商', desc: '管理达人、分配任务、审核内容' },
+  { value: 'creator', label: '达人', desc: '上传脚本和视频、查看审核结果' },
+]
+
+export default function RegisterPage() {
+  const router = useRouter()
+  const { register } = useAuth()
+  const [name, setName] = useState('')
+  const [email, setEmail] = useState('')
+  const [phone, setPhone] = useState('')
+  const [password, setPassword] = useState('')
+  const [confirmPassword, setConfirmPassword] = useState('')
+  const [role, setRole] = useState<UserRole>('creator')
+  const [error, setError] = useState('')
+  const [isLoading, setIsLoading] = useState(false)
+
+  const handleSubmit = async (e: React.FormEvent) => {
+    e.preventDefault()
+    setError('')
+
+    if (!name.trim()) {
+      setError('请输入用户名')
+      return
+    }
+    if (!email && !phone) {
+      setError('请填写邮箱或手机号')
+      return
+    }
+    if (password.length < 6) {
+      setError('密码至少 6 位')
+      return
+    }
+    if (password !== confirmPassword) {
+      setError('两次密码不一致')
+      return
+    }
+
+    setIsLoading(true)
+
+    const result = await register({
+      name: name.trim(),
+      email: email || undefined,
+      phone: phone || undefined,
+      password,
+      role,
+    })
+
+    if (result.success) {
+      switch (role) {
+        case 'creator':
+          router.push('/creator')
+          break
+        case 'agency':
+          router.push('/agency')
+          break
+        case 'brand':
+          router.push('/brand')
+          break
+      }
+    } else {
+      setError(result.error || '注册失败')
+    }
+
+    setIsLoading(false)
+  }
+
+  return (
+    <div className="min-h-screen bg-bg-page flex flex-col items-center justify-center px-6 py-12">
+      <div className="w-full max-w-sm space-y-8">
+        {/* 返回 */}
+        <Link
+          href="/login"
+          className="inline-flex items-center gap-2 text-text-secondary hover:text-text-primary transition-colors"
+        >
+          <ArrowLeft className="w-4 h-4" />
+          返回登录
+        </Link>
+
+        {/* Logo */}
+        <div className="flex items-center gap-3">
+          <div className="w-12 h-12 rounded-xl bg-gradient-to-br from-accent-indigo to-[#4F46E5] flex items-center justify-center shadow-[0px_8px_24px_-4px_rgba(99,102,241,0.4)]">
+            <ShieldCheck className="w-7 h-7 text-white" />
+          </div>
+          <div>
+            <span className="text-2xl font-bold text-text-primary">注册账号</span>
+            <p className="text-sm text-text-secondary">加入秒思智能审核平台</p>
+          </div>
+        </div>
+
+        {/* 注册表单 */}
+        <form onSubmit={handleSubmit} className="space-y-5">
+          {error && (
+            <div className="flex items-center gap-2 p-3 bg-accent-coral/10 text-accent-coral rounded-lg text-sm">
+              <AlertCircle size={16} />
+              {error}
+            </div>
+          )}
+
+          {/* 角色选择 */}
+          <div className="space-y-2">
+            <label className="block text-sm font-medium text-text-primary">选择角色</label>
+            <div className="grid grid-cols-3 gap-2">
+              {roleOptions.map((opt) => (
+                <button
+                  key={opt.value}
+                  type="button"
+                  onClick={() => setRole(opt.value)}
+                  className={`p-3 rounded-xl border text-center transition-all ${
+                    role === opt.value
+                      ? 'border-accent-indigo bg-accent-indigo/10 text-accent-indigo'
+                      : 'border-border-subtle bg-bg-card text-text-secondary hover:bg-bg-elevated'
+                  }`}
+                >
+                  <div className="font-medium text-sm">{opt.label}</div>
+                </button>
+              ))}
+            </div>
+            <p className="text-xs text-text-tertiary">
+              {roleOptions.find((o) => o.value === role)?.desc}
+            </p>
+          </div>
+
+          {/* 用户名 */}
+          <div className="space-y-2">
+            <label className="block text-sm font-medium text-text-primary">用户名</label>
+            <div className="relative">
+              <User className="absolute left-4 top-1/2 -translate-y-1/2 w-5 h-5 text-text-tertiary" />
+              <input
+                type="text"
+                placeholder="请输入用户名"
+                value={name}
+                onChange={(e) => setName(e.target.value)}
+                className="w-full pl-12 pr-4 py-3.5 bg-bg-elevated border border-border-subtle rounded-xl text-text-primary placeholder-text-tertiary focus:outline-none focus:ring-2 focus:ring-accent-indigo focus:border-transparent transition-all"
+                required
+              />
+            </div>
+          </div>
+
+          {/* 邮箱 */}
+          <div className="space-y-2">
+            <label className="block text-sm font-medium text-text-primary">邮箱</label>
+            <div className="relative">
+              <Mail className="absolute left-4 top-1/2 -translate-y-1/2 w-5 h-5 text-text-tertiary" />
+              <input
+                type="email"
+                placeholder="请输入邮箱"
+                value={email}
+                onChange={(e) => setEmail(e.target.value)}
+                className="w-full pl-12 pr-4 py-3.5 bg-bg-elevated border border-border-subtle rounded-xl text-text-primary placeholder-text-tertiary focus:outline-none focus:ring-2 focus:ring-accent-indigo focus:border-transparent transition-all"
+              />
+            </div>
+          </div>
+
+          {/* 手机号 */}
+          <div className="space-y-2">
+            <label className="block text-sm font-medium text-text-primary">
+              手机号 <span className="text-text-tertiary font-normal">(选填)</span>
+            </label>
+            <div className="relative">
+              <Phone className="absolute left-4 top-1/2 -translate-y-1/2 w-5 h-5 text-text-tertiary" />
+              <input
+                type="tel"
+                placeholder="请输入手机号"
+                value={phone}
+                onChange={(e) => setPhone(e.target.value)}
+                className="w-full pl-12 pr-4 py-3.5 bg-bg-elevated border border-border-subtle rounded-xl text-text-primary placeholder-text-tertiary focus:outline-none focus:ring-2 focus:ring-accent-indigo focus:border-transparent transition-all"
+              />
+            </div>
+          </div>
+
+          {/* 密码 */}
+          <div className="space-y-2">
+            <label className="block text-sm font-medium text-text-primary">密码</label>
+            <div className="relative">
+              <Lock className="absolute left-4 top-1/2 -translate-y-1/2 w-5 h-5 text-text-tertiary" />
+              <input
+                type="password"
+                placeholder="至少 6 位密码"
+                value={password}
+                onChange={(e) => setPassword(e.target.value)}
+                className="w-full pl-12 pr-4 py-3.5 bg-bg-elevated border border-border-subtle rounded-xl text-text-primary placeholder-text-tertiary focus:outline-none focus:ring-2 focus:ring-accent-indigo focus:border-transparent transition-all"
+                required
+              />
+            </div>
+          </div>
+
+          {/* 确认密码 */}
+          <div className="space-y-2">
+            <label className="block text-sm font-medium text-text-primary">确认密码</label>
+            <div className="relative">
+              <Lock className="absolute left-4 top-1/2 -translate-y-1/2 w-5 h-5 text-text-tertiary" />
+              <input
+                type="password"
+                placeholder="请再次输入密码"
+                value={confirmPassword}
+                onChange={(e) => setConfirmPassword(e.target.value)}
+                className="w-full pl-12 pr-4 py-3.5 bg-bg-elevated border border-border-subtle rounded-xl text-text-primary placeholder-text-tertiary focus:outline-none focus:ring-2 focus:ring-accent-indigo focus:border-transparent transition-all"
+                required
+              />
+            </div>
+          </div>
+
+          <button
+            type="submit"
+            disabled={isLoading}
+            className="w-full py-3.5 rounded-xl bg-gradient-to-r from-accent-indigo to-[#4F46E5] text-white font-semibold text-base shadow-[0px_8px_24px_-4px_rgba(99,102,241,0.4)] hover:opacity-90 transition-opacity disabled:opacity-50"
+          >
+            {isLoading ? '注册中...' : '注册'}
+          </button>
+        </form>
+
+        {/* 底部链接 */}
+        <p className="text-center text-sm text-text-secondary">
+          已有账号？{' '}
+          <Link href="/login" className="text-accent-indigo hover:underline font-medium">
+            立即登录
+          </Link>
+        </p>
+      </div>
+    </div>
+  )
+}