Add Cloudflare Pages deployment and docs site setup instructions (README update)

[JamesFincher]

Motivation

• Replace the default Next.js boilerplate with project-focused documentation to make this repo a Markdown-first workspace for drafting, reviewing, versioning, and publishing public docs.
• Provide clear, actionable steps to deploy to Cloudflare Pages and map docs.amberprotocol.org, and explain local Convex usage for the versioned content model.

Description

• Rewrote README.md to describe the repo purpose, the draft→final→official workflow, and the Convex-backed content model.
• Added local development instructions using pnpm and a note to run the Convex local dev server via npx convex dev.
• Added step-by-step Cloudflare Pages deployment guidance including build settings and explicit instructions to add the docs.amberprotocol.org custom domain and verify DNS/TLS.
• Included a verification command example (curl -I https://docs.amberprotocol.org).

Testing

• Ran pnpm -s lint, which completed successfully with only warnings reported in generated Convex files.

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Codex Task