bbGuild 2.0.0-rc5

• [FIX] Three non-functional buttons on the ACP Games → List games page — "Create custom game" (addgame2) and the "Default game" Confirm (upddefaultgame) had no POST handler in listgames() (which only assigned template vars and never inspected the request), so both silently did nothing; they are now wired to game::install_game() (custom-install path, with form-token check, length validation, and a duplicate-id guard via ERROR_GAME_EXISTS) and game::update_gamedefault() respectively, and {{ S_FORM_TOKEN }} was added to the default-game form (#371)
• [CHG] Removed the redundant "Install from game plugin" control from the same page — game plugins already register their game automatically on extension enable (each plugin's migrations/basics/data.php seeds the bb_games row via its installer), so the separate ACP "install" step was duplicate work and its addgame1 button was itself dead; the fieldset is renamed "Custom game installation" with the Region dropdown reordered last, and the now-unused gamelistrow/CANINSTALL/PREINSTALLED code was dropped (#371)
• [CHG] All 9 game plugins now hard-require bbGuild core ≥ 2.0.0-rc5 via MIN_BBGUILD_VERSION in each plugin's ext.php::is_enableable(); composer soft-require bumped to >=2.0.0-rc5 (advisory)