Update .gitignore to handle session files and build artifacts

- Added patterns for session files in hm_web/sessions/
- Added patterns for binary files (executables)
- Added patterns for nginx build artifacts

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -18,3 +18,13 @@ cache
 
 player1
 player2
+
+# Session files
+hm_web/sessions/*
+
+# Binary files
+hm_gameserver/hm_gameserver
+hm_lobbyserver/hm_lobbyserver
+
+# Build artifacts
+hm_nginx/objs/*