fix: platform_silent记忆提取 + 群聊上下文整合 + 多QQ实例支持

- platform_silent模式接入Orchestrator记忆提取：被动观察群聊时提取值得记住的信息到对应命名空间
- post_chat后台思考注入平台观察：对话后思考也能看到群聊摘要
- QQ适配器：OneBot v11 self_id动态捕获、CQ图片URL提取、视觉+OCR并行处理
- Router解耦：ConfigName/PlatformName分离，支持多QQ实例独立连接
- 黑白名单功能：后端API + Ethend代理 + UI面板
- \n\n双换行断句：AI回复按双换行分割为多条消息按间隔发送
- @提及修复：bot自感知UID进行@检测
- 群聊上下文共享：channel-based userID避免记忆碎片化
- 消息日志显示处理后内容而非原始SSE数据
- platform-bridge Dockerfile + docker-compose.yml更新

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

backend/platform-bridge/internal/bridge/mapper.go

@@ -44,6 +44,23 @@ func (m *IdentityMapper) Resolve(platform, platformUID string) (*permissions.Pla
 	return id, nil
 }
 
+// ResolveOrNil finds the Cyrene user for a platform identity, returning nil for unknown users.
+func (m *IdentityMapper) ResolveOrNil(platform, platformUID string) *permissions.PlatformIdentity {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	plat, ok := m.byPlatform[platform]
+	if !ok {
+		return nil
+	}
+	return plat[platformUID]
+}
+
+// IsAdmin returns true if the given platform user is a registered admin.
+func (m *IdentityMapper) IsAdmin(platform, platformUID string) bool {
+	id := m.ResolveOrNil(platform, platformUID)
+	return id != nil && id.PermissionLevel == "admin"
+}
+
 // List returns all identities for a platform.
 func (m *IdentityMapper) List(platform string) []permissions.PlatformIdentity {
 	m.mu.RLock()