feat: 频道自动发现 — platform-bridge定时刷新频道路由 + ai-core周期同步

platform-bridge:
- QQ adapter: FetchGroups/FetchFriends 从NapCat API获取
- ChannelLister接口 + ChannelInfo结构体
- GET /api/v1/channels 端点 + cachedChannels缓存
- StartChannelRefresh 每10分钟自动刷新

ai-core:
- channel_sync.go: 每5分钟从platform-bridge拉取频道
- 自动更新thinker的platformChannels + botUIDs
- 不再依赖PLATFORM_CHANNELS环境变量手动配置

修复:
- SendMessage显式设AutoEscape:false
- PLATFORM_BRIDGE_URL默认端口8082→8095
- OBv11Params.AutoEscape去掉omitempty

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

backend/platform-bridge/internal/adapter/qq/adapter.go

@@ -94,18 +94,22 @@ func (a *Adapter) SetGroupName(groupID int64, name string) {
 	a.groupNamesMu.Unlock()
 }
 
+// httpBase derives the HTTP base URL from the WebSocket remote URL.
+func (a *Adapter) httpBase() string {
+	httpBase := strings.Replace(a.remoteURL, "ws://", "http://", 1)
+	httpBase = strings.Replace(httpBase, "wss://", "https://", 1)
+	if idx := strings.LastIndex(httpBase, "/"); idx > 8 {
+		httpBase = httpBase[:idx]
+	}
+	return httpBase
+}
+
 // fetchGroupName tries to resolve a group name via NapCat HTTP API (client mode).
 func (a *Adapter) fetchGroupName(groupID int64) {
 	if a.mode != "client" || a.remoteURL == "" {
 		return
 	}
-	// Derive HTTP base from WS URL: ws://host:port → http://host:port
-	httpBase := strings.Replace(a.remoteURL, "ws://", "http://", 1)
-	httpBase = strings.Replace(httpBase, "wss://", "https://", 1)
-	// Strip path suffix if present
-	if idx := strings.LastIndex(httpBase, "/"); idx > 8 {
-		httpBase = httpBase[:idx]
-	}
+	httpBase := a.httpBase()
 
 	go func() {
 		url := fmt.Sprintf("%s/get_group_info?group_id=%d", httpBase, groupID)