Added

• Command blocking during battles: commands are now blocked by default while a player is in an active battle. Configurable via battle_commands in config.yml with a whitelist of allowed commands (/battle, /msg, /r, /reply, /tell by default). Players with pvpindex.battle.commands.bypass permission can still use all commands. Closes #19.
• New BattleCommandBlockListener in platform-paper that intercepts PlayerCommandPreprocessEvent at LOWEST priority.
• New config section battle_commands in config.yml with block_commands toggle and allowed_commands whitelist.
• New permission pvpindex.battle.commands.bypass (default: op) to bypass command blocking.
• New lang key battle.command_blocked in all bundled language files (en, de, nl, es, pl, zh).