Instead of relying on Icecast's listener IPs (which show proxy IPs
behind HAProxy), capture real client IPs from X-Forwarded-For header
when users visit the front page or audio player frame.
Radiance automatically extracts X-Forwarded-For into (remote *request*).
Changes:
- Add *web-listeners* hash table to track visitors with real IPs
- Add register-web-listener to capture IPs during page requests
- Add collect-geo-stats-from-web-listeners for polling
- Call register-web-listener from front-page and audio-player-frame
- Filter out private/internal IPs (172.x, 192.168.x, 10.x, 127.x)
- Remove session requirement - use IP hash as key for anonymous visitors