optimize codebase

main.go:
- Eliminated ~160 lines of duplicate code: Extracted 3 new helper functions at the bottom of the file:
buildVideoMenuOptions([]VideoOption) — builds the Discord select menu options for video formats
buildAudioMenuOptions([]AudioOption) — same for audio
fetchAndShowFormats(s, i, url) — fetches formats, sorts them, builds menus, stores state, and edits the interaction; previously duplicated identically in both the download and download video command handlers
- Fixed time.Sleep ordering bug: The startAsyncDownload goroutine was launched before InteractionRespond with a 100ms sleep to compensate. Now the download is launched after InteractionRespond returns — no sleep needed. Removed "time" import.
- Used helpers in video_select handler: The two inline menu-building loops in that handler now call buildAudioMenuOptions / buildVideoMenuOptions

misc.go:
- Moved regexp.MustCompile(...) to a package-level var urlPattern — previously it recompiled the regex on every call to extractURLFromString
- Simplified the function body to a single return line

app/go.sum

@@ -14,6 +14,8 @@ github.com/dubyatp/go-ytdlp v0.0.0-20260308044557-db32b29c1590 h1:27d1UwjlfuF/kw
 github.com/dubyatp/go-ytdlp v0.0.0-20260308044557-db32b29c1590/go.mod h1:VgjnTrvkTf+23JuySjyPq1iQ8ijSovBtTPpXH5XrLtI=
 github.com/gorilla/websocket v1.4.2 h1:+/TMaTYc4QFitKJxsQ7Yye35DkWvkdLcvGKqM+x0Ufc=
 github.com/gorilla/websocket v1.4.2/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
+github.com/lrstanley/go-ytdlp v1.3.3 h1:Y9kJcdTwskPWDiwONMIl501Dhi+OrTF7HHY6J6+Lbco=
+github.com/lrstanley/go-ytdlp v1.3.3/go.mod h1:VgjnTrvkTf+23JuySjyPq1iQ8ijSovBtTPpXH5XrLtI=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=