feat(discord): support GOCLAW_DISCORD_TOKEN env var for channel config (#6)

Add env var overlay and auto-enable for Discord channel, matching the
existing Telegram pattern. Update .env.example and docker-compose.yml.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.env.example

@@ -17,6 +17,7 @@ GOCLAW_ENCRYPTION_KEY=
 
 # --- Channels (optional) ---
 GOCLAW_TELEGRAM_TOKEN=
+GOCLAW_DISCORD_TOKEN=
 
 # --- Database (only for non-Docker deployments) ---
 # Docker Compose auto-builds this from POSTGRES_USER/PASSWORD/DB.

docker-compose.yml

@@ -42,6 +42,7 @@ services:
       - GOCLAW_XAI_API_KEY=${GOCLAW_XAI_API_KEY:-}
       # Channels
       - GOCLAW_TELEGRAM_TOKEN=${GOCLAW_TELEGRAM_TOKEN:-}
+      - GOCLAW_DISCORD_TOKEN=${GOCLAW_DISCORD_TOKEN:-}
       # Debug
       - GOCLAW_TRACE_VERBOSE=${GOCLAW_TRACE_VERBOSE:-0}
     volumes:

internal/config/config_load.go

@@ -106,6 +106,7 @@ func (c *Config) applyEnvOverrides() {
 	envStr("GOCLAW_PERPLEXITY_API_KEY", &c.Providers.Perplexity.APIKey)
 	envStr("GOCLAW_GATEWAY_TOKEN", &c.Gateway.Token)
 	envStr("GOCLAW_TELEGRAM_TOKEN", &c.Channels.Telegram.Token)
+	envStr("GOCLAW_DISCORD_TOKEN", &c.Channels.Discord.Token)
 	envStr("GOCLAW_ZALO_TOKEN", &c.Channels.Zalo.Token)
 	envStr("GOCLAW_FEISHU_APP_ID", &c.Channels.Feishu.AppID)
 	envStr("GOCLAW_FEISHU_APP_SECRET", &c.Channels.Feishu.AppSecret)
@@ -122,6 +123,9 @@ func (c *Config) applyEnvOverrides() {
 	if c.Channels.Telegram.Token != "" {
 		c.Channels.Telegram.Enabled = true
 	}
+	if c.Channels.Discord.Token != "" {
+		c.Channels.Discord.Enabled = true
+	}
 	if c.Channels.Zalo.Token != "" {
 		c.Channels.Zalo.Enabled = true
 	}