- Add 3-life system: each death costs a life, game over at 0 lives
- Add game over screen with arcade-style 3-character name entry
- Submit player name with score to analytics backend on game over
- Fix score 0 on leaderboard by periodically stashing stats to JS
so the beforeunload fallback has real data when users close the tab
- Display lives counter in HUD next to health hearts
- Move player respawn control from level.c to main.c via
player_death_pending flag for proper lives tracking
