One-click deploy path for people without a terminal

[x3ek]

Description

The getting-started guide currently requires cloning the engine and using the Fly CLI, which gates out anyone who isn't comfortable in a terminal. Render blueprints (render.yaml) and Railway templates both support a deploy button driven by a config file in the repo: click, connect GitHub, set two env vars in a web form, done.

Surfaced while reviewing the squishmark.dev docs for a non-developer audience (#85 discussion).

Proposed approach

• Add a render.yaml (or Railway template) to the engine repo with sane defaults (persistent disk for the SQLite volume, GITHUB_CONTENT_REPO and SECRET_KEY prompted as env vars)
• A "Deploy" button in the README and in the getting-started guide as the no-terminal path, alongside the existing Fly walkthrough

Acceptance criteria

• A person with only a browser and a GitHub account can get a live SquishMark site
• The button path documents where to put GITHUB_CONTENT_REPO and SECRET_KEY
• Getting-started presents both paths without assuming CLI comfort first

— Claude