feat(web): 将原生 select 替换为 shadcn/ui Select 组件并支持图片消息发送

- 在 AccountForm、AssetGallery、ChatView、ConfigForm、PromptEditor 中将 `<select>` 替换为 shadcn/ui 的 Select 组件以统一 UI 风格
- 在 ChatView 和 useChat hook 中支持发送图片附件
- 更新 pi-bridge 和 ws/chat 以处理 agent 调用中的图片数据

web/client/src/components/assets/AssetGallery.tsx

@@ -4,6 +4,7 @@ import { useAssets } from '@/hooks/useAssets';
 import { AssetProjectGroup } from './AssetProjectGroup';
 import { AssetPreview } from './AssetPreview';
 import { Button } from '@/components/ui/button';
+import { Select, SelectTrigger, SelectValue, SelectContent, SelectItem } from '@/components/ui/select';
 import type { Asset } from '@/types';
 
 interface ManifestGroup {
@@ -125,16 +126,17 @@ export function AssetGallery() {
           ))}
         </div>
 
-        <select
-          value={accountFilter}
-          onChange={(e) => setAccountFilter(e.target.value)}
-          className="h-8 rounded-lg border border-zinc-100 bg-zinc-50/80 px-2 text-xs hover:border-zinc-200 transition-colors"
-        >
-          <option value="">全部账号</option>
-          {accounts.map((a) => (
-            <option key={a.id} value={a.id}>{a.name}</option>
-          ))}
-        </select>
+        <Select value={accountFilter || 'all'} onValueChange={(v) => setAccountFilter(v === 'all' ? '' : v)}>
+          <SelectTrigger className="h-8 w-auto min-w-[100px] text-xs border-zinc-100 bg-zinc-50/80 hover:border-zinc-200">
+            <SelectValue placeholder="全部账号" />
+          </SelectTrigger>
+          <SelectContent>
+            <SelectItem value="all">全部账号</SelectItem>
+            {accounts.map((a) => (
+              <SelectItem key={a.id} value={a.id}>{a.name}</SelectItem>
+            ))}
+          </SelectContent>
+        </Select>
 
         <div className="flex-1" />
         <Button size="sm" variant="outline" className="h-8 text-xs rounded-lg" onClick={handleScan}>