docs: add future stellar.toml metadata plan

[Davidemulo]

Summary

• document the required https://<domain>/.well-known/stellar.toml URL and Next.js public/.well-known/stellar.toml source location
• explain HTTPS, CORS, domain ownership, and issuer home_domain requirements
• separate Testnet and Mainnet account, domain, metadata, and security expectations
• provide clearly non-live placeholder CMOVE metadata and a production-readiness checklist
• link the new guide from the README

No deployable TOML file is added, so the issue's conditional placeholder-file validation script is not required.

Validation

• npm run lint — passes with 2 pre-existing warnings
• npm run typecheck --if-present — passes from a clean generated-output state
• npm run build — passes with pre-existing dependency/schema warnings
• git diff --check

Evidence

Closes #9

[Obiajulu-gif]

@Davidemulo great Job... This looks great