profiler: drop percentage from scan progress line

Show only 'N / total files — path' during 'Profile from card'; the
percentage was redundant. Help docs updated. SW cache v55 -> v56.

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'otaman-v55';
+const CACHE = 'otaman-v56';
 const URLS = [
   'index.html',
   'help.html',