feat: 分组图标统一（iconfont 名字优先，字符兜底）+ 后台选图标

- 新增 components/common/GroupMark：值是图标名就渲染图标，否则按字符显示，
  兼容旧数据里的 emoji；后台的 GroupMark 改为复用同一判断
- 分组详情页 hero 之前把图标名当文本渲染（会直接显示 folder_2_line），已修
- 分组编辑弹窗加「选择图标」：搜索 + 网格，446 个图标按关键字过滤（默认展示前 120）
- 输入框仍可手填字符，旧数据不用迁移

stash-web/src/components/admin/AdminNext.tsx

@@ -25,6 +25,7 @@ import {
 import { useEffect, useMemo, useState } from 'react'
 import { changePassword, fetchSession, logout, type SessionState } from '../../auth'
 import { LoginDialog } from '../auth/LoginDialog'
+import { GroupMark as GroupGlyph } from '../common/GroupMark'
 import {
   fetchSettings,
   saveSettings,
@@ -430,19 +431,18 @@ const FORMAT_LABEL: Record<GroupFormat, string> = {
 }
 
 function GroupMark({ icon }: { icon: string }) {
-  if (icon.trim() === '') {
-    return <span className="group-mark group-mark-empty" aria-hidden="true" />
-  }
-  if (ICON_NAMES.includes(icon as IconName)) {
-    return (
-      <span className="group-mark" aria-hidden="true">
-        <Icon name={icon as IconName} />
-      </span>
-    )
-  }
+  const value = icon.trim()
+  const isIcon = ICON_NAMES.includes(value as IconName)
+  const classes = [
+    'group-mark',
+    value === '' ? 'group-mark-empty' : isIcon ? '' : 'group-mark-text',
+  ]
+    .filter(Boolean)
+    .join(' ')
+
   return (
-    <span className="group-mark group-mark-text" aria-hidden="true">
-      {icon}
+    <span className={classes} aria-hidden="true">
+      <GroupGlyph icon={icon} />
     </span>
   )
 }
@@ -632,6 +632,16 @@ function GroupDialog({
   const [enabled, setEnabled] = useState(true)
   const [busy, setBusy] = useState(false)
   const [error, setError] = useState('')
+  const [iconPickerOpen, setIconPickerOpen] = useState(false)
+  const [iconQuery, setIconQuery] = useState('')
+
+  // 图标库里 446 个名字，先按关键字过滤，没输入时只给前 120 个，避免一次渲染太多
+  const iconList = useMemo(() => {
+    const query = iconQuery.trim().toLowerCase()
+    const names =
+      query === '' ? ICON_NAMES : ICON_NAMES.filter((name) => name.includes(query))
+    return names.slice(0, 120)
+  }, [iconQuery])
 
   useEffect(() => {
     if (!open) return
@@ -787,7 +797,11 @@ function GroupDialog({
           </FormField>
         )}
 
-        <FormField label="图标样式" htmlFor="group-icon" hint="留空则不显示图标；可填 iconfont 图标名或一个字符">
+        <FormField
+          label="图标"
+          htmlFor="group-icon"
+          hint="从图标库选一个，或直接填一个字符（旧数据里的 emoji 照旧显示）"
+        >
           <div className="group-icon-field">
             <span className="group-icon-preview">
               <GroupMark icon={icon} />
@@ -795,10 +809,47 @@ function GroupDialog({
             <Input
               id="group-icon"
               value={icon}
-              placeholder="如 folder_line / 📁，留空不显示"
+              placeholder="如 folder_2_line / 📁，留空不显示"
               onChange={(event) => setIcon(event.target.value)}
             />
+            <Button variant="secondary" onClick={() => setIconPickerOpen((open) => !open)}>
+              选择图标
+            </Button>
           </div>
+          {iconPickerOpen && (
+            <div className="icon-picker">
+              <Input
+                value={iconQuery}
+                placeholder="搜索图标名，如 folder / user / play"
+                icon="search_3_line"
+                clearable
+                onClear={() => setIconQuery('')}
+                onChange={(event) => setIconQuery(event.target.value)}
+              />
+              <div className="icon-picker-grid">
+                {iconList.map((name) => (
+                  <button
+                    key={name}
+                    type="button"
+                    className="icon-picker-item"
+                    title={name}
+                    aria-label={name}
+                    onClick={() => {
+                      setIcon(name)
+                      setIconPickerOpen(false)
+                    }}
+                  >
+                    <Icon name={name} />
+                  </button>
+                ))}
+              </div>
+              {iconList.length === 0 && (
+                <Text size="sm" tone="muted">
+                  没有匹配的图标，换个关键字试试。
+                </Text>
+              )}
+            </div>
+          )}
         </FormField>
 
         <div className="group-dialog-row">