Review breakdown: show each deck's own activity total

Follow-up to the smart-review breakdown: "I only have 2 decks" turned out to
be three deck cards (one clipped at the window edge) and 15 + 13 + 6 = 34
due. The line now carries each deck's activity total next to its due count -
"Due by deck: Sky deck - 15 of 15 - Humanismus - 13 of 15 - ... - 6 of 13" -
so the arithmetic is checkable inline without opening a deck.

groupByDeck returns {label, count, total}; new i18n key review.dueOfTotal
(en + cs). review-test pins the format. Version 0.6.9, SW v91.

tests/review-test.mjs

@@ -189,7 +189,7 @@ async function makeReviewPage(locale = "en") {
   );
   check(
     "review: the card breaks the count down by deck",
-    breakdown === "Due by deck: Sky deck · 2 · Twin deck · 2",
+    breakdown === "Due by deck: Sky deck · 2 of 2 · Twin deck · 2 of 2",
     breakdown,
   );