feat: add Docker env var support for PORT, HOST, and TEMPERATURE

- Add port and host fields to GatewayConfig with defaults (3000, 127.0.0.1)
- Enhanced apply_env_overrides() to support:
  - ZEROCLAW_GATEWAY_PORT or PORT - Gateway server port
  - ZEROCLAW_GATEWAY_HOST or HOST - Gateway bind address
  - ZEROCLAW_TEMPERATURE - Default temperature (0.0-2.0)
- Add comprehensive tests for all new env var overrides
- Fix clippy warnings (is_multiple_of, too_many_lines)

Closes #45

src/tools/browser.rs

@@ -366,6 +366,7 @@ impl BrowserTool {
 }
 
 #[async_trait]
+#[allow(clippy::too_many_lines)]
 impl Tool for BrowserTool {
     fn name(&self) -> &str {
         "browser"