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/handler/channel_refresh.go

@@ -0,0 +1,59 @@
+package handler
+
+import (
+	"log"
+	"net/http"
+	"time"
+
+	"git.yeij.top/AskaEth/Cyrene/platform-bridge/internal/bridge"
+)
+
+// listChannels returns cached channels from all adapters (groups + friends).
+// GET /api/v1/channels
+func (h *BridgeHandler) listChannels(w http.ResponseWriter, r *http.Request) {
+	h.channelsMu.RLock()
+	channels := h.cachedChannels
+	h.channelsMu.RUnlock()
+	if channels == nil {
+		channels = []bridge.ChannelInfo{}
+	}
+	writeJSON(w, http.StatusOK, map[string]interface{}{
+		"channels": channels,
+		"total":    len(channels),
+	})
+}
+
+// StartChannelRefresh periodically queries all adapters for their channel lists.
+func (h *BridgeHandler) StartChannelRefresh(interval time.Duration) {
+	if interval <= 0 {
+		interval = 10 * time.Minute
+	}
+	go func() {
+		ticker := time.NewTicker(interval)
+		defer ticker.Stop()
+		log.Printf("[channel-refresh] 频道缓存刷新已启动 (间隔=%v)", interval)
+		h.refreshChannels()
+		for range ticker.C {
+			h.refreshChannels()
+		}
+	}()
+}
+
+// refreshChannels queries all ChannelLister adapters and updates the cache.
+func (h *BridgeHandler) refreshChannels() {
+	var all []bridge.ChannelInfo
+	for _, name := range h.router.ListAdapters() {
+		a, err := h.router.GetAdapter(name)
+		if err != nil {
+			continue
+		}
+		if lister, ok := a.(bridge.ChannelLister); ok {
+			channels := lister.ListChannels()
+			all = append(all, channels...)
+		}
+	}
+	h.channelsMu.Lock()
+	h.cachedChannels = all
+	h.channelsMu.Unlock()
+	log.Printf("[channel-refresh] 频道缓存已更新: %d 个频道", len(all))
+}