Improve README presentation

[alianjum0]

Summary

• improve the README opening with a product screenshot, defensive-fetching rationale, request flow, and architecture diagram
• reorganize the existing technical documentation into clearer portfolio-oriented sections without removing its implementation detail
• pin proxy-addr 2.0.8 through a pnpm override to clear the newly reported critical production audit finding

Validation

• pnpm verify — passed syntax checks, 61 tests, and production audit with no known vulnerabilities
• git diff --check — passed
• screenshot captured from and visually checked against the local application

Risks and notes

• no public demo link was added because the repository has no verified deployment URL and the previous Heroku deployment returns 404
• the dependency change is limited to the patched proxy-addr 2.0.8 transitive resolution