Add version check warning for network play

[MostCromulent]

Summary

• Client now sends its Forge version to the server as part of the login handshake
• Server compares client version against host version when a player joins
• If versions differ, a chat warning is displayed advising players to use the same version to avoid network compatibility issues

Requested by @tool4ever in #9642 — small standalone PR to give hosts visibility over potential version mismatches before they cause problems.

Details

Adds a version field to LoginEvent, populated with BuildInfo.getVersionString(). The server checks it in LobbyInputHandler after the player is assigned a lobby slot. Three cases:

Scenario	Result
Versions match	Silent (no message)
Versions differ	Warning: "PlayerName is using Forge version X (host: Y). Please use the same version as the host to avoid network compatibility issues."
Old client (no version field)	Warning: "Could not determine PlayerName's Forge version..."

Backward compatible — serialVersionUID is unchanged, so old clients/servers handle the new field gracefully (defaults to null).

3 files changed, +24 −2 lines.

Test plan

• Compile check passes (0 checkstyle violations)
• Manually tested version mismatch warning by hardcoding a fake version on the client
• Simulated CI locally (mvn -U -B clean test) — all 13 modules pass

🤖 Generated with Claude Code

[tool4ever]

thanks