Keep auto-center enabled by default

Previously auto-center was turned off after the first GPS fix.
Now it stays on, keeping the map centered on the player's position.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

index.html

@@ -4208,11 +4208,7 @@
             if (gpsFirstFix) {
                 map.setView([lat, lng], 17);
                 gpsFirstFix = false;
-                // After first fix, turn off auto-center (user must manually enable)
-                autoCenterMode = false;
-                const btn = document.getElementById('autoCenterBtn');
-                btn.textContent = 'Auto-Center: OFF';
-                btn.classList.remove('active');
+                // Keep auto-center on by default
             } else if (autoCenterMode) {
                 map.setView([lat, lng], map.getZoom());
             }