Fix: Cancel button now aborts in-flight text message requests

[divyansh-cyber]

The Cancel button did not abort in-flight text message requests. Only the timeout could stop them the AbortSignal from the UI was ignored. This PR fixes that by combining the caller’s signal with the timeout signal in callChatbotApi, so user cancel and timeout both abort the request.
Problem
callChatbotApi always used its own timeout AbortController, overwriting the caller’s options.signal.
Result: clicking Cancel didn’t abort text requests; they ran until completion or timeout.

Solution
Respect the caller’s options.signal.
Combine it with the timeout using AbortSignal.timeout() and AbortSignal.any().
Pass the combined (or timeout-only) signal to fetch so Cancel and timeout both work.

Changes

callChatbotApi.ts: Combine caller + timeout signals, pass to fetch, use strict AbortError check, remove manual timers.
callChatbotApi.test.ts: Add test to verify abort on caller signal.

Testing

Unit tests pass, including cancel test.

Fixes: #135

[divyansh-cyber]

@berviantoleo all checks have passed,Is there anything else you'd like me to adjust