feat(discord): add listen_to_bots config and fix model IDs across codebase (#280)

* fix(config): apply env overrides at runtime and fix Docker compose defaults

- Call apply_env_overrides() after Config::load_or_init() in main.rs so
  environment variables (API_KEY, PROVIDER, ZEROCLAW_GATEWAY_PORT, etc.)
  are actually applied at runtime, not just in tests
- Add ZEROCLAW_ALLOW_PUBLIC_BIND env var support for gateway bind policy
- Fix docker-compose.yml: correct volume path (/zeroclaw-data not /data),
  add ZEROCLAW_ALLOW_PUBLIC_BIND=true for container networking, make host
  port configurable via HOST_PORT env var
- Add docker-compose.override.yml to .gitignore for local dev overrides

* feat(discord): add listen_to_bots config and fix model IDs across codebase

Add listen_to_bots field to DiscordConfig so bot messages are processed
when explicitly enabled (defaults to false for backward compat). Remove
ZEROCLAW_MODEL from Dockerfile release stage so config.toml is the
source of truth for model selection. Fix all hardcoded model IDs from
the dated anthropic/claude-sonnet-4-20250514 to the valid OpenRouter
identifier anthropic/claude-sonnet-4.

src/config/schema.rs

@@ -774,6 +774,10 @@ pub struct DiscordConfig {
     pub guild_id: Option<String>,
     #[serde(default)]
     pub allowed_users: Vec<String>,
+    /// When true, process messages from other bots (not just humans).
+    /// The bot still ignores its own messages to prevent feedback loops.
+    #[serde(default)]
+    pub listen_to_bots: bool,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -887,7 +891,7 @@ impl Default for Config {
             config_path: zeroclaw_dir.join("config.toml"),
             api_key: None,
             default_provider: Some("openrouter".to_string()),
-            default_model: Some("anthropic/claude-sonnet-4-20250514".to_string()),
+            default_model: Some("anthropic/claude-sonnet-4".to_string()),
             default_temperature: 0.7,
             observability: ObservabilityConfig::default(),
             autonomy: AutonomyConfig::default(),