feat: 添加账号支持选择学习平台

账号新增 platform 字段，登录/刷新课程/发现课程按平台分发；同时把 JS 脚本收进 script/（目录规范调整）。

web/src/App.tsx

@@ -75,6 +75,7 @@ function accountPayload(account: Account) {
   return {
     id: account.id,
     username: account.username,
+    platform: account.platform || 'guanyixue',
     note: account.note || '',
     user: account.user || '',
     cookies: account.cookies || [],
@@ -93,6 +94,9 @@ export default function App() {
   const [accounts, setAccounts] = useState<Account[]>([])
   const accountsRef = useRef(accounts)
   const [platforms, setPlatforms] = useState<Record<string, string>>({ guanyixue: '莞易学' })
+  const [platformList, setPlatformList] = useState<PlatformInfo[]>([
+    { id: 'guanyixue', label: '莞易学' },
+  ])
   const [offline, setOffline] = useState(false)
   const [toast, setToast] = useState<ToastState | null>(null)
   const [pending, setPending] = useState<Record<string, string>>({})
@@ -193,9 +197,12 @@ export default function App() {
   useEffect(() => {
     api<{ platforms: PlatformInfo[] }>('/api/platforms')
       .then((response) => {
+        const list = response.platforms || []
+        if (!list.length) return
+        setPlatformList(list)
         const map: Record<string, string> = {}
-        for (const platform of response.platforms || []) map[platform.id] = platform.label
-        if (Object.keys(map).length) setPlatforms(map)
+        for (const platform of list) map[platform.id] = platform.label
+        setPlatforms(map)
       })
       .catch(() => {})
   }, [])
@@ -366,7 +373,10 @@ export default function App() {
       try {
         let response = await api<CoursesResponse>('/api/courses', {
           method: 'POST',
-          body: JSON.stringify({ cookies: account.cookies }),
+          body: JSON.stringify({
+            cookies: account.cookies,
+            platform: account.platform || 'guanyixue',
+          }),
         })
         if (!response.ok && response.code === 'session_expired') {
           notify({ message: '会话已失效，正在自动重新登录…' })
@@ -578,6 +588,7 @@ export default function App() {
       method: 'POST',
       body: JSON.stringify({
         username: data.username,
+        platform: data.platform,
         password: data.password,
         note: data.note,
         cookies: [],
@@ -621,7 +632,8 @@ export default function App() {
   }
 
   function platformLabel(account: Account) {
-    const id = (account.courses || []).find((course) => course.platform)?.platform
+    const id =
+      account.platform || (account.courses || []).find((course) => course.platform)?.platform
     return (id && platforms[id]) || '莞易学'
   }
 
@@ -749,6 +761,7 @@ export default function App() {
 
       <AddAccountDialog
         open={dialog?.type === 'add'}
+        platforms={platformList}
         onClose={() => setDialog(null)}
         onSubmit={addAccount}
       />