feat: Add DingTalk channel support via Stream Mode

- Add pkg/channels/dingtalk.go with WebSocket Stream Mode
- Add DingTalkConfig to config.go
- Register DingTalk in manager.go
- Update README with DingTalk setup instructions
- Add open-dingtalk/dingtalk-stream-sdk-go v0.9.1 dependency

pkg/config/config.go

@@ -36,6 +36,7 @@ type ChannelsConfig struct {
 	Feishu   FeishuConfig   `json:"feishu"`
 	Discord  DiscordConfig  `json:"discord"`
 	MaixCam  MaixCamConfig  `json:"maixcam"`
+	DingTalk DingTalkConfig `json:"dingtalk"`
 }
 
 type WhatsAppConfig struct {
@@ -72,6 +73,13 @@ type MaixCamConfig struct {
 	AllowFrom []string `json:"allow_from" env:"PICOCLAW_CHANNELS_MAIXCAM_ALLOW_FROM"`
 }
 
+type DingTalkConfig struct {
+	Enabled          bool     `json:"enabled" env:"PICOCLAW_CHANNELS_DINGTALK_ENABLED"`
+	ClientID         string   `json:"client_id" env:"PICOCLAW_CHANNELS_DINGTALK_CLIENT_ID"`
+	ClientSecret     string   `json:"client_secret" env:"PICOCLAW_CHANNELS_DINGTALK_CLIENT_SECRET"`
+	AllowFrom        []string `json:"allow_from" env:"PICOCLAW_CHANNELS_DINGTALK_ALLOW_FROM"`
+}
+
 type ProvidersConfig struct {
 	Anthropic  ProviderConfig `json:"anthropic"`
 	OpenAI     ProviderConfig `json:"openai"`
@@ -146,6 +154,12 @@ func DefaultConfig() *Config {
 				Port:      18790,
 				AllowFrom: []string{},
 			},
+			DingTalk: DingTalkConfig{
+				Enabled:      false,
+				ClientID:     "",
+				ClientSecret: "",
+				AllowFrom:    []string{},
+			},
 		},
 		Providers: ProvidersConfig{
 			Anthropic:  ProviderConfig{},