FULL SCREEN MODERN ANIMATION UPGRADE

Added full-screen animation layer for overlay replay events.

Changed files:
- overlay.php
- assets/css/overlay.css
- assets/js/overlay.js

Supported events:
- FOUR
- SIX
- WICKET
- WIN
- FIFTY
- CUSTOM / any other text

How it works:
Dashboard replay buttons and score buttons still set match_state.replay_event.
Overlay detects replay_event and plays a 2.7 second full-screen animation.
After animation, api/clear_replay.php clears the event.

OBS URL stays same:
http://localhost/point3/overlay.php