docs: related-tools section, language links, and RU wording polish

- Add a 'Related tools' section (EN + RU) introducing SIMple, SIMtrace
  Analyser and sigrok_iso7816_stream as independent tools.
- Cross-link the two READMEs (English/Russian) at the top.
- Russian: replace the 'pill' calque with 'button' (README_RUS + help-ru),
  and tighten the PC/SC-fallback, init-output and canonical-path wording.
- Bump the SW cache for the help-ru.html change.

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'simple-v488';
+const CACHE = 'simple-v489';
 const URLS = [
   'index.html',
   'help.html',