fix(plugins): 插件管理 - 修正官方应用插件的分类与状态显示

AI 审美分析和剪辑工作台在管理页显示为"已停用"，原因是三处插件
分类清单不一致：

- 后端 officialApplicationPolicies 缺少 editor-shell
- 管理页 officialApplicationIds 同时缺少 ai-art-critique 和 editor-shell
- 用户插件页另有一份重复清单

后端把这两个插件当作系统协议处理（Kind=protocol），platformAvailable
回退为 false，于是返回"管理员已停用该插件"，管理页据此渲染成"已停用"。

修复：

- 后端补上 editor-shell 应用策略（权威修复，决定平台可用性）
- 前端抽取唯一清单 OFFICIAL_APPLICATION_PLUGIN_IDS，管理页与用户插件页
  共用，删除两份重复实现
- 补前后端回归测试，锁定这 8 个官方应用插件

验证：tsc --noEmit 通过；前端 17 项测试通过；后端 TestEditorShell* 与
既有插件测试通过；前后端镜像构建通过。

backend/internal/app/plugin_management_test.go

@@ -76,3 +76,44 @@ func TestArtCritiqueIsUserToggleableApplication(t *testing.T) {
 		t.Fatalf("AI art critique policy = %#v", policy)
 	}
 }
+
+// Regression: editor-shell was missing from officialApplicationPolicies, so the
+// backend classified it as a system protocol and reported it to the admin page
+// as "管理员已停用该插件" even though nothing disabled it.
+func TestEditorShellIsUserToggleableApplication(t *testing.T) {
+	policy := pluginManagement(PluginEditorShell, "bundled")
+	if policy.Origin != PluginOriginOfficial || policy.Kind != PluginKindApplication || policy.ActivationScope != PluginScopeUser || policy.ConfigurationScope != PluginConfigurationNone {
+		t.Fatalf("editor shell policy = %#v", policy)
+	}
+}
+
+func TestEditorShellReportsPlatformAvailableWithoutPlatformState(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open("file:"+newID()+"?mode=memory&cache=shared"), &gorm.Config{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := db.AutoMigrate(&model.PluginPlatformState{}, &model.UserPluginState{}, &model.AdminAuditEvent{}); err != nil {
+		t.Fatal(err)
+	}
+	center, err := newPluginRuntime(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	svc := &Service{repo: repository.New(db), pluginRuntime: center}
+	user := &model.User{ID: "user-1", Role: model.UserRoleUser}
+
+	states, err := svc.PluginStatesForUser(user)
+	if err != nil {
+		t.Fatal(err)
+	}
+	state, ok := states[PluginEditorShell]
+	if !ok {
+		t.Fatalf("editor shell missing from plugin states: %#v", states)
+	}
+	if !state.PlatformAvailable || !state.CanToggle {
+		t.Fatalf("editor shell should be a user-toggleable application, got %#v", state)
+	}
+	if state.BlockedReason == "管理员已停用该插件" {
+		t.Fatalf("editor shell reported as admin-disabled: %#v", state)
+	}
+}