Added rates proxy backend (Cloudflare Workers)

[gonfff]

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[Copilot]

Pull request overview

This PR adds a currency rates proxy backend built with Python for Cloudflare Workers. The implementation follows clean architecture principles with distinct domain, application, infrastructure, and presentation layers. The proxy fetches exchange rates from Yahoo Finance, implements rate limiting and caching, and exposes a REST API at /v1/rates.

Changes:

• Complete backend implementation with domain-driven design
• Comprehensive test suite with good coverage across all layers
• Configuration for Cloudflare Workers deployment via wrangler

Reviewed changes

Copilot reviewed 33 out of 39 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
backend/wrangler.jsonc	Cloudflare Workers configuration with environment variables
backend/pyproject.toml	Python project configuration with dependencies and dev tools
backend/src/worker.py	Worker entry point that handles HTTP requests
backend/src/rates/*	Core application code organized in layers (domain/application/infrastructure/presentation)
backend/tests/*	Comprehensive test suite covering all layers
backend/package.json	NPM configuration for wrangler deployment scripts
backend/uv.lock	Python dependency lock file

Files not reviewed (1)

• backend/package-lock.json: Language not supported

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