feat: 为所有终端添加平台显示功能

- 新增 frontend/lib/platforms.ts 共享平台配置模块
- 支持6个平台: 抖音、小红书、B站、快手、微博、微信视频号
- 品牌方终端: 项目看板、项目详情、终审台列表添加平台显示
- 代理商终端: 工作台概览、审核台、Brief配置、达人管理、
  数据报表、消息中心、申诉处理添加平台显示
- 达人端: 任务列表添加平台显示
- 统一使用彩色头部条样式展示平台信息

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/app/brand/projects/create/page.tsx

@@ -14,9 +14,20 @@ import {
   X,
   Users,
   Search,
-  Building2
+  Building2,
+  Check
 } from 'lucide-react'
 
+// 平台选项
+const platformOptions = [
+  { id: 'douyin', name: '抖音', icon: '🎵', color: 'bg-[#1a1a1a]' },
+  { id: 'xiaohongshu', name: '小红书', icon: '📕', color: 'bg-[#fe2c55]' },
+  { id: 'bilibili', name: 'B站', icon: '📺', color: 'bg-[#00a1d6]' },
+  { id: 'kuaishou', name: '快手', icon: '⚡', color: 'bg-[#ff4906]' },
+  { id: 'weibo', name: '微博', icon: '🔴', color: 'bg-[#e6162d]' },
+  { id: 'wechat', name: '微信视频号', icon: '💬', color: 'bg-[#07c160]' },
+]
+
 // 模拟品牌方已添加的代理商（来自代理商管理）
 const mockAgencies = [
   { id: 'AG789012', name: '星耀传媒', companyName: '上海星耀文化传媒有限公司', creatorCount: 50, passRate: 92 },
@@ -33,6 +44,7 @@ export default function CreateProjectPage() {
   const [deadline, setDeadline] = useState('')
   const [briefFile, setBriefFile] = useState<File | null>(null)
   const [selectedAgencies, setSelectedAgencies] = useState<string[]>([])
+  const [selectedPlatform, setSelectedPlatform] = useState<string>('')
   const [isSubmitting, setIsSubmitting] = useState(false)
   const [agencySearch, setAgencySearch] = useState('')
 
@@ -60,7 +72,7 @@ export default function CreateProjectPage() {
   }
 
   const handleSubmit = async () => {
-    if (!projectName.trim() || !deadline || !briefFile || selectedAgencies.length === 0) {
+    if (!projectName.trim() || !deadline || !briefFile || selectedAgencies.length === 0 || !selectedPlatform) {
       alert('请填写完整信息')
       return
     }
@@ -72,7 +84,7 @@ export default function CreateProjectPage() {
     router.push('/brand')
   }
 
-  const isValid = projectName.trim() && deadline && briefFile && selectedAgencies.length > 0
+  const isValid = projectName.trim() && deadline && briefFile && selectedAgencies.length > 0 && selectedPlatform
 
   return (
     <div className="space-y-6 max-w-4xl">
@@ -100,6 +112,38 @@ export default function CreateProjectPage() {
             />
           </div>
 
+          {/* 选择平台 */}
+          <div>
+            <label className="block text-sm font-medium text-text-primary mb-2">
+              发布平台 <span className="text-accent-coral">*</span>
+            </label>
+            <p className="text-xs text-text-tertiary mb-3">选择视频将发布的平台，系统将应用对应平台的审核规则</p>
+            <div className="grid grid-cols-3 md:grid-cols-6 gap-3">
+              {platformOptions.map((platform) => (
+                <button
+                  key={platform.id}
+                  type="button"
+                  onClick={() => setSelectedPlatform(platform.id)}
+                  className={`p-3 rounded-xl border-2 transition-all flex flex-col items-center gap-2 ${
+                    selectedPlatform === platform.id
+                      ? 'border-accent-indigo bg-accent-indigo/10'
+                      : 'border-border-subtle hover:border-accent-indigo/50'
+                  }`}
+                >
+                  <div className={`w-10 h-10 ${platform.color} rounded-lg flex items-center justify-center text-lg`}>
+                    {platform.icon}
+                  </div>
+                  <span className="text-sm font-medium text-text-primary">{platform.name}</span>
+                  {selectedPlatform === platform.id && (
+                    <div className="absolute top-1 right-1 w-4 h-4 rounded-full bg-accent-indigo flex items-center justify-center">
+                      <Check size={10} className="text-white" />
+                    </div>
+                  )}
+                </button>
+              ))}
+            </div>
+          </div>
+
           {/* 截止日期 */}
           <div>
             <label className="block text-sm font-medium text-text-primary mb-2">