Initial commit: Chat-to-diagram v1.0

- Chat interface with OpenAI GPT integration
- Automatic diagram generation from text descriptions
- Tldraw canvas with Dagre layout engine
- REST API instead of WebSocket approach

🤖 Generated with Claude Code (https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,6 @@
+# OpenAI API Configuration (NEXT_PUBLIC_ prefix required for client-side access)
+NEXT_PUBLIC_OPENAI_API_KEY=your_openai_api_key_here
+OPENAI_API_KEY=your_openai_api_key_here
+
+# Optional: Custom WebSocket Relay URL (if not using the built-in relay)
+# NEXT_PUBLIC_WS_URL=ws://localhost:3000/api/realtime