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/bridge_handler.go

@@ -7,14 +7,17 @@ import (
 	"net/http"
 	"os"
 	"strconv"
+	"sync"
 
 	"git.yeij.top/AskaEth/Cyrene/platform-bridge/internal/bridge"
 )
 
 // BridgeHandler exposes the Platform Bridge REST API.
 type BridgeHandler struct {
-	router        *bridge.PlatformRouter
-	internalToken string
+	router         *bridge.PlatformRouter
+	internalToken  string
+	channelsMu     sync.RWMutex
+	cachedChannels []bridge.ChannelInfo
 }
 
 func NewBridgeHandler(router *bridge.PlatformRouter) *BridgeHandler {
@@ -30,6 +33,7 @@ func (h *BridgeHandler) RegisterRoutes(mux *http.ServeMux) {
 	mux.HandleFunc("/api/v1/platforms/", h.platformInfo)
 	mux.HandleFunc("/api/v1/identities", h.listIdentities)
 	mux.HandleFunc("/api/v1/internal/send-proactive", h.sendProactive)
+	mux.HandleFunc("/api/v1/channels", h.listChannels)
 	mux.HandleFunc("/api/v1/webhook/telegram", h.telegramWebhook)
 	mux.HandleFunc("/api/v1/webhook/", h.genericWebhook)
 }