fix(input): handle Ctrl+C via SIGINT signal instead of keypress

[chiranjeevi-max]

Fixes #487

Previously, bandwhich intercepted Ctrl+C as a keyboard event, which caused it to exit even when users had disabled SIGINT via stty intr ^-.

Now uses the ctrlc crate to properly handle the SIGINT signal. The q key remains as the keyboard-based quit option.

[chiranjeevi-max]

I noticed a hang issue when receiving a SIGINT.
=> the handler sets running = false, but the terminal_event_handler thread was blocked indefinitely on crossterm::event::read().
=> Since read() is a blocking call, the thread never got a chance to check the running flag, causing the app to hang on SIGINT.

The Fix:

• I used poll() with 100ms timeout instead of blocking read() in TerminalEvents::next() and also change the event loop to check running flag between poll timeouts.
• Add terminal cleanup after start() returns to restore terminal state on SIGINT exit

[cyqsimon]

Don't worry about the Windows test failures. CI downloads npcap but for some reason it's unreliable. Haven't had time to check why yet.

[cyqsimon]

Thanks!