feat: backfill name/QTH/grid/address from the last QSO when lookup finds nothing

When a callsign resolves only to cty.dat (not on QRZ/HamQTH, or no lookup service
configured) — or the lookup errors — enrich the entry from the most recent QSO
already in the log with that call. Fills ONLY the fields the provider left empty
and the operator hasn't edited (name, QTH, grid, country, address, state, county,
lat/lon, zones, continent, email, QSL-via), so a real QRZ/HamQTH hit is never
overridden. Uses the worked-before entries (qso_date DESC, [0] = latest) via a
live ref so it works regardless of the lookup/worked-before debounce ordering.

changelog.json

@@ -3,6 +3,7 @@
     "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.",
@@ -18,6 +19,7 @@
       "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.",