feat(config): 运行时配置体系②——渠道配置落 channels.json + 面板落盘 + 热更新

- runtimeconfig/channels.go: channels.json 承载 map[platform][]ChannelAccount(token/baseURL/黑白名单/群聊限流), LoadChannels 优先文件/回退env, SaveChannels(0600+tmp原子写), Upsert/Delete/Masked脱敏
- channelbridge/reload.go: adapterManager 热替换——工厂重建新adapter先连接, 再原子断旧adapter(独立readCtx/进行中不中断); Bridge.Reload(platform) 逐账号增删
- 面板 PUT/DELETE /admin/channels/{platform}/config(owner+审计) 落盘channels.json+Reload热更新; GET /admin/channels 附账号掩码不泄裸token
- 前端 Channels.tsx 配置表单(id/token/baseURL/黑白名单/限流+config JSON)+保存热更新提示+掩码展示/删除
- .gitignore 加 channels.json; .env 退兜底(.env.example注明); token不打印/Config()脱敏
- channelbridge.go 拆 logic→reload.go(742→731); 全仓 go build/vet/test绿+前端build绿
- 未做真token端到端(需渠道凭据,不读.env)——如实标注待凭据

internal/services/gateway/server.go

@@ -157,6 +157,22 @@ type BackthinkStore interface {
 	List(ctx context.Context, limit int) ([]backthink.Record, error)
 }
 
+// ChannelConfigStore is the runtime-editable channel-adapter configuration
+// (channels.json, design/04 §3.1). It is implemented by the composition root's
+// channel store: Load returns the effective per-platform accounts (file → env
+// fallback), Path reports the channels.json path, and Reload hot-replaces a
+// platform's running adapters after a panel save (Bridge.Reload). Load returns
+// account configs with real tokens so the owner write path can persist them; the
+// admin read path masks them before returning to the client.
+type ChannelConfigStore interface {
+	Path() string
+	// Load returns the effective per-platform accounts (file → env fallback),
+	// including the secret tokens needed to persist them.
+	Load() map[string][]config.ChannelAccount
+	// Reload rebuilds and hot-replaces the running adapters for platform.
+	Reload(platform string) error
+}
+
 // RagStore backs the admin knowledge-base RAG module (design/10 §3.12 module 8).
 // *runtime/knowledge.Store is the production implementation. Every method is
 // read-only for this milestone: IndexDocument/DeleteDocument return a clear
@@ -222,6 +238,10 @@ type Deps struct {
 	// Optional: when nil the admin /llm endpoints fall back to the env config so
 	// pre-existing gateway tests keep working.
 	LLM *model.RuntimeLLM
+	// Channels is the runtime-editable channel-adapter config (channels.json).
+	// Optional: when nil the admin /channels/config endpoints return a clear
+	// not-configured error, matching how the LLM stack behaves when unset.
+	Channels ChannelConfigStore
 	// AuditStore persists the admin audit trail (observability → audit). When nil
 	// the gateway degrades to an in-memory store so the endpoint still returns
 	// data; the composition root injects NewSQLiteAuditStore over a.db for real
@@ -270,6 +290,7 @@ type Server struct {
 	// admin /llm endpoints fall back to the env config. It is optional so tests
 	// that do not wire it keep working.
 	llm      *model.RuntimeLLM
+	channels ChannelConfigStore
 	webhooks map[string]http.Handler
 	log      *slog.Logger
 	hub      *hub
@@ -306,6 +327,7 @@ func New(cfg *config.Config, deps Deps) (*Server, error) {
 		streaming:   deps.Streaming,
 		frontend:    deps.Frontend,
 		llm:         deps.LLM,
+		channels:    deps.Channels,
 		webhooks:    deps.Webhooks,
 		log:         sourcedLog(deps.Log),
 	}
@@ -385,6 +407,8 @@ func (s *Server) Handler() http.Handler {
 	mux.Handle("POST /api/v1/admin/channels/open", ownerAuth(http.HandlerFunc(s.adminChannelOpen)))
 	mux.Handle("POST /api/v1/admin/channels/close", ownerAuth(http.HandlerFunc(s.adminChannelClose)))
 	mux.Handle("POST /api/v1/admin/channels/test", ownerAuth(http.HandlerFunc(s.adminChannelTest)))
+	mux.Handle("PUT /api/v1/admin/channels/{platform}/config", ownerAuth(http.HandlerFunc(s.adminSaveChannelConfig)))
+	mux.Handle("DELETE /api/v1/admin/channels/{platform}/config", ownerAuth(http.HandlerFunc(s.adminDeleteChannelAccount)))
 	mux.Handle("POST /api/v1/admin/plugins/install", ownerAuth(http.HandlerFunc(s.adminPluginInstall)))
 	mux.Handle("POST /api/v1/admin/plugins/uninstall", ownerAuth(http.HandlerFunc(s.adminPluginUninstall)))
 	mux.Handle("POST /api/v1/admin/memories", ownerAuth(http.HandlerFunc(s.adminAddMemory)))