feat: prefer the last QSO's precise locator over the cty.dat centroid; changelog → 0.21.2

For an entity resolved only via cty.dat (e.g. a French call not on QRZ/HamQTH),
the provider block sets a coarse country-centroid grid. The worked-before backfill
now overrides that with the precise locator from the last QSO with this call, and
takes that QSO's lat/lon (derived from the grid when the record stored none) so
the map and saved record stay consistent. A real provider grid still wins.

Moved the (unreleased) worked-before backfill entry into a new 0.21.2 changelog
block, since 0.21.1 is already out.

changelog.json

@@ -1,9 +1,18 @@
 [
+  {
+    "version": "0.21.2",
+    "date": "2026-07-25",
+    "en": [
+      "When a callsign isn't found on QRZ/HamQTH (or you don't use a lookup service), the name, QTH, locator and address are recovered from the last time you worked that station — and the precise locator from that QSO is used instead of the coarse cty.dat country centroid. A real QRZ/HamQTH hit still wins."
+    ],
+    "fr": [
+      "Quand un indicatif est introuvable sur QRZ/HamQTH (ou si tu n'utilises pas de service de lookup), le nom, le QTH, le locator et l'adresse sont récupérés du dernier QSO avec cette station — et c'est le locator précis de ce QSO qui est utilisé, pas le centroïde du pays de cty.dat. Un vrai résultat QRZ/HamQTH reste prioritaire."
+    ]
+  },
   {
     "version": "0.21.1",
     "date": "2026-07-24",
     "en": [
-      "When a callsign isn't found on QRZ/HamQTH (or you don't use a lookup service), the name, QTH, grid and address are now recovered from the last time you worked that station — provider data still wins when there is a hit.",
       "Ctrl + mouse wheel zoom is now remembered across restarts (Ctrl+0 resets to 100%).",
       "Log grid: award column widths are now saved like the other columns, so a width you set survives a restart.",
       "CW keyer widget: added an F9 macro slot, and empty macros are now hidden (like the voice keyer) — fill them in Settings → CW Keyer.",
@@ -19,7 +28,6 @@
       "Fixed award references (in the entry strip's Awards tab) not clearing when the callsign changes — clicking one spot then another no longer keeps the previous station's references."
     ],
     "fr": [
-      "Quand un indicatif est introuvable sur QRZ/HamQTH (ou si tu n'utilises pas de service de lookup), le nom, le QTH, le locator et l'adresse sont maintenant récupérés du dernier QSO avec cette station — les données du service restent prioritaires en cas de résultat.",
       "Le zoom Ctrl + molette est maintenant conservé après un redémarrage (Ctrl+0 remet à 100 %).",
       "Grille du log : les largeurs des colonnes de diplômes sont désormais sauvegardées comme les autres colonnes, une largeur réglée survit au redémarrage.",
       "Widget keyer CW : ajout d'un emplacement de macro F9, et les macros vides sont maintenant masquées (comme le keyer vocal) — remplis-les dans Réglages → Keyer CW.",