Add initial implementation of ePage application with Docker support

- Create main application logic with HTTP handlers for form submissions
- Implement Pushover API integration for sending messages
- Add unit tests for handlers and Pushover payload structure
- Include Dockerfile and docker-compose configuration for easy deployment
- Add example environment file and update README with setup instructions
- Create HTML templates for user interface

.env.example

@@ -0,0 +1,6 @@
+# Example environment file
+# Copy this to .env and fill in your actual values
+
+PUSHOVER_API_TOKEN=your_api_token_here
+PUSHOVER_USER_KEY=your_user_key_here
+PORT=5000