Add SELKIES_UI_TITLE to upstream-confirmed LinuxServer Selkies GUI apps so the sidebar title can be configured from the 1Panel install form while preserving the upstream default.
Also update modmanager upgrade scripts to honor MODCACHE_PATH instead of hardcoding ./data/modcache.
Validation: git diff --check; static audit issues=0; path script audit issues=0; docker compose config failures=0; 1Panel smoke passed for firefox-linuxserver latest and webtop-linuxserver latest.
okxlin