Add "Copy as cURL" button to request detail view

[agaonker]

Summary

• Adds a "Copy as cURL" button in the request detail header bar
• Converts intercepted HTTP requests (method, URL, headers, body)
  into a valid curl command and copies it to the clipboard
• Shows brief "Copied!" feedback after clicking

Changes

• src/lib/curl.ts — New utility to convert a Flow into a curl command string. Handles method, headers, body, shell escaping, and multiline formatting.
• src/components/detail/RequestSection.tsx — Added the copy button between the URL and the view mode toggle.

Test plan

• Start proxy (npm run dev:server) and dashboard (npm run dev)
• Send requests through the proxy (e.g. curl -x http://localhost:9090 http://httpbin.org/get)
• Click an intercepted request in the sidebar
• Click "Copy as cURL" in the request header bar
• Paste into terminal and verify the generated curl command is valid and reproduces the original request
• Verify POST requests with headers and JSON body produce correct output

Screenshots