fix: #16 sortOption 接入后端排序 API

- KnowledgeItemService.list 加 sortBy/order 参数
- loadItems/refresh/loadMore 加 sortBy/order 参数
- sortOption onChange 触发重新加载
- sortParams 映射函数: 0→默认, 1→fileSize, 2→createdAt, 3→updatedAt

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

AIStudyApp/AIStudyApp/Core/Services/APIService.swift

@@ -149,10 +149,11 @@ class KnowledgeItemService {
     static let shared = KnowledgeItemService()
     private let client = APIClient.shared
 
-    func list(knowledgeBaseId: String) async throws -> [KnowledgeItem] {
+    func list(knowledgeBaseId: String, sortBy: String? = nil, order: String? = nil) async throws -> [KnowledgeItem] {
-        return try await client.request("/knowledge-items", queryItems: [
+        var items = [URLQueryItem(name: "knowledgeBaseId", value: knowledgeBaseId)]
-            URLQueryItem(name: "knowledgeBaseId", value: knowledgeBaseId),
+        if let s = sortBy { items.append(URLQueryItem(name: "sortBy", value: s)) }
-        ])
+        if let o = order { items.append(URLQueryItem(name: "order", value: o)) }
+        return try await client.request("/knowledge-items", queryItems: items)
     }
 
     func detail(id: String) async throws -> KnowledgeItem {

AIStudyApp/AIStudyApp/Features/Library/LibrarySubpages.swift

@@ -392,6 +392,10 @@ struct LibraryDetailPage: View {
             Text("确定要删除选中的 \(selectedIds.count) 个知识点吗？此操作不可恢复。")
         }
         .task { await viewModel.loadItems(knowledgeBaseId: knowledgeBaseId) }
+        .onChange(of: sortOption) { _ in
+            let (sb, od) = sortParams(sortOption)
+            Task { await viewModel.loadItems(knowledgeBaseId: knowledgeBaseId, sortBy: sb, order: od) }
+        }
         .safeAreaInset(edge: .bottom) {
             NavigationLink(value: Route.aiChat(context: ChatEntryContext(scopeType: .knowledgeBase, scopeId: knowledgeBaseId, scopeName: "知识库", parentKnowledgeBaseId: knowledgeBaseId, createdFrom: "knowledge_base_detail"))) {
                 HStack(spacing: 8) {
@@ -496,6 +500,15 @@ struct LibraryDetailPage: View {
         return URL(string: "https://longde.cloud\(urlString)")
     }
 
+    private func sortParams(_ option: Int) -> (String?, String?) {
+        switch option {
+        case 1: return ("fileSize", "desc")
+        case 2: return ("createdAt", "desc")
+        case 3: return ("updatedAt", "desc")
+        default: return (nil, nil)
+        }
+    }
+
     private func fileTypeText(for item: KnowledgeItem) -> String {
         if let t = item.sourceType?.trimmingCharacters(in: .whitespaces), !t.isEmpty {
             return t.uppercased()

AIStudyApp/AIStudyApp/Features/Library/LibraryViewModel.swift

@@ -92,13 +92,13 @@ class LibraryDetailViewModel: ObservableObject {
     private var currentPage = 1
     private let pageSize = 20
 
-    func loadItems(knowledgeBaseId: String) async {
+    func loadItems(knowledgeBaseId: String, sortBy: String? = nil, order: String? = nil) async {
         isLoading = true
         errorMessage = nil
         currentPage = 1
         do {
             async let kb = try? KnowledgeBaseService.shared.detail(id: knowledgeBaseId)
-            async let list = try? KnowledgeItemService.shared.list(knowledgeBaseId: knowledgeBaseId)
+            async let list = try? KnowledgeItemService.shared.list(knowledgeBaseId: knowledgeBaseId, sortBy: sortBy, order: order)
             let (kbResult, listResult) = await (kb, list)
             knowledgeBase = kbResult
             items = listResult ?? []
@@ -109,22 +109,22 @@ class LibraryDetailViewModel: ObservableObject {
         isLoading = false
     }
 
-    func refresh(knowledgeBaseId: String) async {
+    func refresh(knowledgeBaseId: String, sortBy: String? = nil, order: String? = nil) async {
         isRefreshing = true
         currentPage = 1
         do {
-            items = try await KnowledgeItemService.shared.list(knowledgeBaseId: knowledgeBaseId)
+            items = try await KnowledgeItemService.shared.list(knowledgeBaseId: knowledgeBaseId, sortBy: sortBy, order: order)
             hasMore = items.count >= pageSize
         } catch {}
         isRefreshing = false
     }
 
-    func loadMore(knowledgeBaseId: String) async {
+    func loadMore(knowledgeBaseId: String, sortBy: String? = nil, order: String? = nil) async {
         guard !isLoadingMore, hasMore else { return }
         isLoadingMore = true
         currentPage += 1
         do {
-            let more = try await KnowledgeItemService.shared.list(knowledgeBaseId: knowledgeBaseId)
+            let more = try await KnowledgeItemService.shared.list(knowledgeBaseId: knowledgeBaseId, sortBy: sortBy, order: order)
             items.append(contentsOf: more)
             hasMore = more.count >= pageSize
         } catch {