Run TypeScript compilation in Joplin Server scripts

Added 'yarn run tsc' to both update and install scripts for Joplin Server to ensure TypeScript sources are compiled. Also removed an unused variable from build.func for code cleanup.

misc/build.func

@@ -4508,7 +4508,6 @@ create_lxc_container() {
     fi
 
     ONLINE_TEMPLATES=()
-    ONLINE_TEMPLATE=""
     mapfile -t ONLINE_TEMPLATES < <(pveam available -section system 2>/dev/null | grep -E '\.(tar\.zst|tar\.xz|tar\.gz)$' | awk '{print $2}' | grep -E "^${TEMPLATE_SEARCH}.*${TEMPLATE_PATTERN}" | sort -t - -k 2 -V 2>/dev/null || true)
     [[ ${#ONLINE_TEMPLATES[@]} -gt 0 ]] && ONLINE_TEMPLATE="${ONLINE_TEMPLATES[-1]}"