Update documentation with continuous deployment instructions

[clue]

Builds on top of https://github.com/clue-engineering/eventbridge/pull/21 (private), https://github.com/clue-engineering/justkanban-website/pull/4 (private) and #127
Refs #145

[Copilot]

Pull Request Overview

This PR updates the README documentation to provide clearer instructions for continuous deployment setup. The changes expand the deployment documentation to include CDN options and add detailed steps for setting up the CI/CD infrastructure.

Key changes:

• Updated deployment section to mention CDN (Bunny CDN) as an alternative to reverse proxy
• Enhanced continuous deployment section with detailed setup instructions
• Renamed "Auto-Deployment" section to "Continuous Deployment" for clarity

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