checked dependencies, made some optional, document optional dependencies

profile.d/filefct.sh

@@ -471,6 +471,12 @@ file_stats()
     fi
 
     # Minimum/maximum size filters (evaluated in bytes)
+    if [[ -n "$min_size" || -n "$max_size" ]]; then
+        if ! command -v numfmt >/dev/null 2>&1; then
+            disp E "file_stats: --min/--max require 'numfmt' (GNU coreutils). Please install it."
+            return 1
+        fi
+    fi
     if [[ -n "$min_size" ]]; then
         find_cmd+=(-size +"$(numfmt --from=iec "$min_size")"c)
     fi