feat: harden user file handling and gate LaunchServices rebuild (#159)

- add ensure_user_dir/ensure_user_file helpers in lib/core/base.sh, including
  sudo-aware ownership correction under the invoking user’s home
- use the helpers across clean/optimize/purge/uninstall/whitelist to create
  cache and export files safely (no naked mkdir/touch), including log files and
  dry-run exports
- ensure purge stats/count files and update message caches are pre-created with
  safe permissions
- add Darwin version helpers and skip LaunchServices/dyld rebuild on macOS 15+,
  keeping the existing corruption protection for earlier versions
- guard brew cache timestamp writes and TCC permission flags with safe file
  creation to avoid root-owned artifacts

bin/clean.sh

@@ -159,6 +159,7 @@ start_section() {
 
     # Write section header to export list in dry-run mode
     if [[ "$DRY_RUN" == "true" ]]; then
+        ensure_user_file "$EXPORT_LIST_FILE"
         echo "" >> "$EXPORT_LIST_FILE"
         echo "=== $1 ===" >> "$EXPORT_LIST_FILE"
     fi
@@ -452,7 +453,7 @@ start_cleanup() {
         SYSTEM_CLEAN=false
 
         # Initialize export list file
-        mkdir -p "$(dirname "$EXPORT_LIST_FILE")"
+        ensure_user_file "$EXPORT_LIST_FILE"
         cat > "$EXPORT_LIST_FILE" << EOF
 # Mole Cleanup Preview - $(date '+%Y-%m-%d %H:%M:%S')
 #