Files view: the update row's change link is "Show diff" (v2.6.5)

- an update row whose image changed (or whose bytes were first observed)
  offered a generic "Details" link; it now says "Show diff" — Russian
  «Изменения» — while a card-side change keeps its "Changed on card!" link
  (both open the same change modal)
- the now-unused 'Details' RU key is gone; tests update the wiring pin and
  the Russian-translation list; 527 Python + 61 Node tests
- README/README_RUS mention the new label; PWA_VERSION/pyproject/version.py
  2.6.5, SW cache simtrace-analyser-v79

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'simtrace-analyser-v78';
+const CACHE = 'simtrace-analyser-v79';
 
 const PRECACHE = [
     'index.html',