Added rates proxy backend (Cloudflare Workers)

backend/.gitignore

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+# Logs
+
+logs
+_.log
+npm-debug.log_
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+.pnpm-debug.log*
+
+# Diagnostic reports (https://nodejs.org/api/report.html)
+
+report.[0-9]_.[0-9]_.[0-9]_.[0-9]_.json
+
+# Runtime data
+
+pids
+_.pid
+_.seed
+\*.pid.lock
+
+# Dependency directories
+
+node_modules/
+jspm_packages/
+
+# TypeScript cache
+
+\*.tsbuildinfo
+
+# Optional npm cache directory
+
+.npm
+
+# Optional eslint cache
+
+.eslintcache
+
+# Optional stylelint cache
+
+.stylelintcache
+
+# Optional REPL history
+
+.node_repl_history
+
+# Output of 'npm pack'
+
+\*.tgz
+
+# public
+
+# Stores VSCode versions used for testing VSCode extensions
+
+.vscode-test
+
+# wrangler project
+
+.dev.vars*
+!.dev.vars.example
+.env*
+!.env.example
+.wrangler/
+
+# python-specific
+python_modules/
+.venv/
+.venv-workers/
+.python-version
+__pycache__/
+.mypy_cache/
+.pytest_cache/

backend/README.md

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+# Subctrl Rates Proxy
+
+In the future, I might separate this into a separate service.
+
+Local development uses uv and FastAPI.
+
+```bash
+uv sync
+uv tool run --from workers-py pywrangler dev
+```
+
+The API is versioned under `/v1` and expects `base` + `quotes` query params.
+
+## Configuration
+
+Backend details and deployment instructions live in `docs/pages/proxy-backend.md`.
+
+Default proxy configuration (from `backend/wrangler.jsonc`):
+
+- `CACHE_MAX_AGE_SECONDS=10800` (3 hours, cache TTL for `/v1/rates` responses).
+- `RATE_LIMIT_MAX=50` (max requests per IP in the window).
+- `RATE_LIMIT_WINDOW_SECONDS=60` (rate limit window in seconds).
+- `UPSTREAM_TIMEOUT_SECONDS=6` (timeout for Yahoo upstream requests).
+
+
+# [tool.uv.scripts]
+# format = "ruff check --select I --fix . && ruff format ."
+# lint = "ruff check . && mypy src"