fix(ios): M1 审查修复 3 个 Bug

- AIChatPage 会话列表按钮补充 .sheet 展示历史对话
- AIChatViewModel 新增 loadSession() 加载对话历史
- NotificationListView 日期解析兼容多种 ISO 格式

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

AIStudyApp/AIStudyApp/Features/AI/AIChatPage.swift

@@ -77,6 +77,34 @@ struct AIChatPage: View {
                 }
             }
         }
+        .sheet(isPresented: $showSessions) {
+            VStack(spacing: 0) {
+                RoundedRectangle(cornerRadius: 3).fill(Color.zxF03).frame(width: 36, height: 5).padding(.top, 12).padding(.bottom, 16)
+                Text("对话列表").font(.system(size: 16, weight: .semibold)).foregroundColor(Color.zxF0).padding(.bottom, 16)
+                if sessions.isEmpty {
+                    Text("暂无历史对话").font(.system(size: 14)).foregroundColor(Color.zxF04).padding(.top, 40)
+                } else {
+                    ScrollView {
+                        VStack(spacing: 0) {
+                            ForEach(sessions) { s in
+                                Button {
+                                    showSessions = false
+                                    Task { await vm.loadSession(s.id) }
+                                } label: {
+                                    HStack {
+                                        Text(s.title ?? "对话").font(.system(size: 14)).foregroundColor(Color.zxF0)
+                                        Spacer()
+                                        Text(s.updatedAt?.prefix(10).description ?? "").font(.system(size: 11)).foregroundColor(Color.zxF04)
+                                    }.padding(.horizontal, 20).padding(.vertical, 14)
+                                }.foregroundColor(.primary)
+                            }
+                        }
+                    }
+                }
+            }
+            .frame(maxWidth: .infinity, maxHeight: .infinity).background(Color.zxBg0)
+            .presentationDetents([.medium, .large])
+        }
         .task { await vm.load() }
     }
 

AIStudyApp/AIStudyApp/Features/AI/AIChatViewModel.swift

@@ -85,7 +85,17 @@ final class AIChatViewModel: ObservableObject {
         }
     }
 
-    func setKnowledgeBase(_ id: String) {
-        knowledgeBaseId = id
+    func setKnowledgeBase(_ id: String) { knowledgeBaseId = id }
+
+    func loadSession(_ id: String) async {
+        sessionId = id
+        isCreatingSession = true
+        do {
+            let msgs: [ChatMessage] = try await RagChatService.shared.getMessages(sessionId: id)
+            messages = msgs.map { m in
+                AIMessage(role: m.role == "user" ? .user : .ai, content: m.content, citations: m.citations)
+            }
+        } catch { sessionError = "加载对话失败" }
+        isCreatingSession = false
     }
 }

AIStudyApp/AIStudyApp/Features/Profile/NotificationListView.swift

@@ -83,12 +83,17 @@ struct NotificationListView: View {
 
     private func isToday(_ dateStr: String?) -> Bool {
         guard let d = dateStr else { return false }
-        let today = ISO8601DateFormatter().string(from: Date())
-        return d.prefix(10) == today.prefix(10)
+        let f = DateFormatter(); f.dateFormat = "yyyy-MM-dd"
+        let today = f.string(from: Date())
+        return d.prefix(10) == today
     }
 
     private func isThisWeek(_ dateStr: String?) -> Bool {
-        guard let d = dateStr, let date = ISO8601DateFormatter().date(from: String(d.prefix(19)) + "Z") else { return false }
+        guard let d = dateStr else { return false }
+        // Backend returns ISO 8601 or MySQL datetime
+        let clean = d.prefix(19).replacingOccurrences(of: "T", with: " ")
+        let f = DateFormatter(); f.dateFormat = "yyyy-MM-dd HH:mm:ss"
+        guard let date = f.date(from: String(clean)) else { return false }
         return Date().timeIntervalSince(date) < 7 * 86400
     }
 }