[ENV-5] Document RunPod env configuration for Nano Banana

- Add comprehensive RunPod deployment guide
- Document environment variable setup in RunPod template UI
- Explain differences between local and RunPod configurations
- Include security notes and verification steps

RUNPOD_SETUP.md

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+# RunPod Deployment Configuration
+
+This document describes how to configure environment variables for ComfyUI when deploying to RunPod Serverless.
+
+## Environment Variables Setup
+
+### Required: Google API Key for Nano Banana
+
+1. Go to [RunPod Console](https://www.runpod.io/console/serverless)
+2. Navigate to **Templates** → Select your ComfyUI template → **Edit**
+3. Scroll to **Environment Variables** section
+4. Add the following variable:
+   - **Key**: `GOOGLE_API_KEY`
+   - **Value**: Your Google AI API key (get one from [Google AI Studio](https://aistudio.google.com/app/apikey))
+
+### Optional: Vertex AI Configuration
+
+If you prefer to use Vertex AI instead of the Google AI API:
+
+- **Key**: `PROJECT_ID`
+- **Value**: Your GCP project ID
+- **Key**: `LOCATION`
+- **Value**: `us-central1` (or your preferred region)
+
+**Note:** Vertex AI requires Application Default Credentials (ADC) to be configured in your container image.
+
+### Optional: OpenTelemetry Configuration
+
+For observability and monitoring:
+
+- **Key**: `OTEL_EXPORTER_OTLP_ENDPOINT`
+- **Value**: `http://your-otel-collector:4317`
+- **Key**: `OTEL_SERVICE_NAME`
+- **Value**: `comfyui`
+- **Key**: `OTEL_RESOURCE_ATTRIBUTES`
+- **Value**: `service.name=comfyui`
+
+## How It Works
+
+The ComfyUI Docker image is configured to read environment variables directly from `os.environ`, which means:
+
+1. **Local Development**: Variables are loaded from `.env` file via `docker-compose.yml`
+2. **RunPod Deployment**: Variables are set in the RunPod template interface
+3. **Code Compatibility**: No code changes needed—both methods use `os.environ`
+
+## Verification
+
+After setting the environment variables in RunPod:
+
+1. Deploy or restart your serverless endpoint
+2. Check the logs for "GOOGLE_API_KEY" to verify it's set
+3. Test Nano Banana nodes to confirm authentication works
+
+## Differences from Local Setup
+
+| Aspect | Local (Docker Compose) | RunPod Serverless |
+|--------|----------------------|-------------------|
+| **Config Method** | `.env` file | RunPod template UI |
+| **GPU Support** | Optional (can run CPU mode) | Typically GPU-enabled |
+| **Persistence** | Docker volumes | RunPod storage |
+| **API Key Storage** | Local `.env` (gitignored) | RunPod environment vars |
+
+## Security Notes
+
+- Environment variables in RunPod are encrypted at rest
+- Never commit `.env` files with real API keys to Git
+- Rotate your API keys periodically
+- Use different API keys for development vs production if possible
+