feat: Integration Hub for external tool connectivity

- Add native config option: `new Brainy({ integrations: true })`
- OData integration for Excel Power Query and Power BI
- Google Sheets integration with Apps Script
- Server-Sent Events (SSE) for real-time streaming
- Webhooks for push notifications
- Zero-config with sensible defaults
- Full tree-shaking when disabled

src/integrations/sse/index.ts

@@ -0,0 +1,12 @@
+/**
+ * SSE (Server-Sent Events) Integration Module
+ *
+ * Provides real-time streaming of Brainy events.
+ * Works in all environments.
+ */
+
+export {
+  SSEIntegration,
+  integration,
+  type SSEConfig
+} from './SSEIntegration.js'