♻️ Refactor watchOS content view

ios/WatchRunner Watch App/ViewModels/ActivityViewModel.swift

@@ -0,0 +1,47 @@
+//
+//  ActivityViewModel.swift
+//  WatchRunner Watch App
+//
+//  Created by LittleSheep on 2025/10/29.
+//
+
+import Foundation
+import Combine
+
+// MARK: - View Models
+
+@MainActor
+class ActivityViewModel: ObservableObject {
+    @Published var activities: [SnActivity] = []
+    @Published var isLoading = false
+    @Published var errorMessage: String?
+
+    private let networkService = NetworkService()
+    let filter: String
+    private var isMock = false
+    
+    init(filter: String, mockActivities: [SnActivity]? = nil) {
+        self.filter = filter
+        if let mockActivities = mockActivities {
+            self.activities = mockActivities
+            self.isMock = true
+        }
+    }
+
+    func fetchActivities(token: String, serverUrl: String) async {
+        if isMock { return }
+        guard !isLoading else { return }
+        isLoading = true
+        errorMessage = nil
+
+        do {
+            let fetchedActivities = try await networkService.fetchActivities(filter: filter, token: token, serverUrl: serverUrl)
+            self.activities = fetchedActivities
+        } catch {
+            self.errorMessage = error.localizedDescription
+            print("[watchOS] fetchActivities failed with error: \(error)")
+        }
+
+        isLoading = false
+    }
+}