fix(chat): actually play the classic Skype emoticon sounds

The whole playback pipeline (viewport one-shot, click-to-replay, prefs
mute toggle) shipped long ago, but skypeSoundUrl pointed at
public/skype-sounds/ and the audio archive was never wired up — so the
feature failed silently on every emoticon since day one.

Classic Skype only ever had EVENT sounds, never per-emoticon audio, so
this maps the nine emoticons with a natural counterpart (skype→IM pop,
call→ring-in, phone→ring-out, hi→login, sleepy→logout, wait→hold,
talktothehand→busy, mail→sent, handshake→contact-added) and serves the
files from the deployment CDN instead of the repo — they are Microsoft
IP and stay out of source distribution. VITE_SKYPE_SOUNDS_BASE lets a
self-hoster point at their own copies.