fix(ios): 创建知识库页面 - 创建后自动返回 + 成功/失败反馈

- 新增 @Environment(\.dismiss) 创建成功后自动返回列表
- 新增 isCreating 加载态，按钮显示 ProgressView 并禁用
- 空名称时按钮灰色不可点击
- 成功 toast "知识库已创建" + 自动 dismiss
- 失败 toast "创建失败，请重试"

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

AIStudyApp/AIStudyApp/Features/Library/LibrarySubpages.swift

@@ -1,15 +1,38 @@
 import SwiftUI
 
 struct CreateLibraryPage: View {
-    @State private var name = ""; @State private var desc = ""
+    @Environment(\.dismiss) private var dismiss
+    @State private var name = ""; @State private var desc = ""; @State private var isCreating = false
     var body: some View {
         ZStack { Color.zxBg0.ignoresSafeArea(); VStack(spacing: 0) {
             ScrollView { VStack(spacing: 20) {
                 VStack(alignment: .leading, spacing: 8) { Text("知识库名称").font(.system(size: 12, weight: .semibold)).foregroundColor(Color.zxF035); TextField("例如：机器学习", text: $name).font(.system(size: 15)).tint(Color.zxPurple).padding(.horizontal, 16).frame(height: 52).background(Color.zxFill004).clipShape(RoundedRectangle(cornerRadius: 14)).overlay(RoundedRectangle(cornerRadius: 14).stroke(Color.zxBorder008, lineWidth: 1)) }
                 VStack(alignment: .leading, spacing: 8) { Text("描述（可选）").font(.system(size: 12, weight: .semibold)).foregroundColor(Color.zxF035); TextField("简单描述这个知识库的内容", text: $desc).font(.system(size: 15)).tint(Color.zxPurple).padding(.horizontal, 16).frame(height: 52).background(Color.zxFill004).clipShape(RoundedRectangle(cornerRadius: 14)).overlay(RoundedRectangle(cornerRadius: 14).stroke(Color.zxBorder008, lineWidth: 1)) }
                 Button {
-                    Task { _ = try? await KnowledgeBaseService.shared.create(title: name, description: desc.isEmpty ? nil : desc) }
+                    guard !name.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty else { return }
-                } label: { Text("创建").font(.system(size: 14, weight: .bold)).foregroundColor(.white).frame(maxWidth: .infinity).frame(height: 52).background(ZXGradient.ctaPurple).clipShape(RoundedRectangle(cornerRadius: 16)) }
+                    isCreating = true
+                    Task {
+                        let kb = try? await KnowledgeBaseService.shared.create(title: name, description: desc.isEmpty ? nil : desc)
+                        await MainActor.run {
+                            isCreating = false
+                            if kb != nil {
+                                ZXToastManager.shared.success("知识库已创建")
+                                dismiss()
+                            } else {
+                                ZXToastManager.shared.error("创建失败，请重试")
+                            }
+                        }
+                    }
+                } label: {
+                    HStack(spacing: 8) {
+                        if isCreating { ProgressView().tint(.white) }
+                        Text("创建").font(.system(size: 14, weight: .bold))
+                    }
+                    .foregroundColor(.white).frame(maxWidth: .infinity).frame(height: 52)
+                    .background(name.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty ? Color.zxHairlineStrong : ZXGradient.ctaPurple)
+                    .clipShape(RoundedRectangle(cornerRadius: 16))
+                }
+                .disabled(isCreating || name.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
             }.padding(.horizontal, 20).padding(.top, 20) }.scrollIndicators(.hidden) }
         }.navigationBarTitleDisplayMode(.inline).toolbarBackground(.hidden, for: .navigationBar)}
 }