fix(fleet): downgrade version from 13 to 12 in configuration files and scripts

fix(invidious): correct indentation in version retrieval
fix(fleet-install): switch from MariaDB to MySQL setup and update database creation logic
fix(tools): add MySQL repository handling in helper functions

ct/invidious.sh

@@ -46,7 +46,7 @@ function update_script() {
 
     msg_info "Rebuilding Invidious"
     cd /opt/invidious
-      INVIDIOUS_VERSION="$(cat ~/.invidious 2>/dev/null || echo "unknown")"
+    INVIDIOUS_VERSION="$(cat ~/.invidious 2>/dev/null || echo "unknown")"
     INVIDIOUS_VERSION="${INVIDIOUS_VERSION#v}"
     sed -i \
       -e "s~^\(\s*CURRENT_BRANCH\s*=\).*~\1 \"master\"~" \