fix(i18n): seventeen strings had drifted into English only

Reported from a photograph of a French screen: "Spot lifetime" and "Chase new
grids" still in English in the DX Cluster settings. Diffing the two dictionaries
turned up fifteen more — including the ENTIRE update panel, which is why an
operator who reads French had nothing in French to react to when a new version
appeared.

All seventeen translated. Both dictionaries now hold 2685 keys with no
difference either way.

Every user-visible string ships in both languages: that was a rule, and until
now only a rule. A test parses the two dictionary literals and compares their
keys, so the next one is caught by `go test` instead of by an operator
photographing their own screen. Verified it fails when a key is removed.

A key missing from one side is not a blank — it falls back to the key itself,
so the interface reads "clu.spotTtl" where a label belongs, or keeps the English
text, which looks deliberate and is not.

changelog.json

@@ -5,12 +5,14 @@
     "en": [
       "Opening the Awards panel no longer pulls the whole logbook several times at once — a large log briefly took gigabytes of memory.",
       "Awards: the Missing refs button now only appears where it means something — a worldwide award like POTA could only ever answer “nothing found”.",
-      "Worked before: a prefixed call like ZA/OE8NDR matched every other visitor to that country instead of that one operator."
+      "Worked before: a prefixed call like ZA/OE8NDR matched every other visitor to that country instead of that one operator.",
+      "French: seventeen strings were still in English, the whole update panel among them, plus Spot lifetime and Chase new grids."
     ],
     "fr": [
       "Ouvrir le panneau Awards ne tire plus plusieurs fois le journal entier en même temps — un gros log occupait brièvement des gigaoctets de mémoire.",
       "Awards : le bouton Réf. manquantes n’apparaît plus que là où il a un sens — un diplôme mondial comme POTA ne pouvait répondre que « aucun manque ».",
-      "Déjà contacté : un indicatif préfixé comme ZA/OE8NDR rapprochait tous les autres visiteurs du pays au lieu de ce seul opérateur."
+      "Déjà contacté : un indicatif préfixé comme ZA/OE8NDR rapprochait tous les autres visiteurs du pays au lieu de ce seul opérateur.",
+      "Français : dix-sept textes étaient restés en anglais, dont tout le panneau de mise à jour, la durée de vie des spots et Chasser les nouveaux locators."
     ]
   },
   {