fix(gui): route runtime status messages through Loc instead of hardcoded Italian

Send/Donate/Sync/Wizard view models wrote status/error strings
directly in Italian ("Importo non valido.", "Errore: …", the TLS
pin-mismatch message, …), so a user running the app in English/German/
etc. still saw them in Italian despite the 6-language Loc system
covering the rest of the UI.

Added the missing Loc keys and routed every occurrence through
Loc.Tr(...). CertificatePinMismatchException (Core) no longer bakes an
Italian message into .Message; it now exposes Host/Port so the UI can
translate it, with an English fallback for any exception type the UI
doesn't specifically handle. Also drops the now-stale USERGUIDE.md
caveat about a few messages staying in Italian regardless of language.

src/App/Localization/Loc.cs

@@ -403,6 +403,24 @@ public sealed class Loc
             "Certificados SSL redefinidos: tente novamente a conexão.",
             "SSL-Zertifikate zurückgesetzt: Verbindung erneut versuchen."],
         ["msg.error"]             = ["Errore",                                                            "Error",                        "Error",                                "Erreur",                                   "Erro",                                     "Fehler"],
+        ["msg.broadcast.error"]   = ["Errore broadcast",                                                  "Broadcast error",              "Error de transmisión",                 "Erreur de diffusion",                      "Erro de transmissão",                      "Übertragungsfehler"],
+        ["msg.peer.discovery.error"] = ["Errore nella scoperta peer",                                     "Peer discovery error",         "Error al descubrir peers",             "Erreur de découverte des pairs",           "Erro na descoberta de peers",              "Fehler bei der Peer-Suche"],
+        ["msg.peer.discovery.found"] = ["Trovati {0} nuovi server dai peer (totale {1}).",                "Found {0} new servers from peers (total {1}).", "Se encontraron {0} nuevos servidores de peers (total {1}).", "{0} nouveaux serveurs trouvés via les pairs (total {1}).", "Encontrados {0} novos servidores dos peers (total {1}).", "{0} neue Server von Peers gefunden (insgesamt {1})."],
+        ["msg.peer.discovery.none"] = ["Nessun nuovo server annunciato (totale {0}).",                    "No new servers announced (total {0}).", "No se anunciaron nuevos servidores (total {0}).", "Aucun nouveau serveur annoncé (total {0}).", "Nenhum novo servidor anunciado (total {0}).", "Keine neuen Server angekündigt (insgesamt {0})."],
+        ["msg.send.sync.first"]  = ["Sincronizza prima di inviare.",                                     "Synchronize before sending.",  "Sincroniza antes de enviar.",          "Synchronisez avant d'envoyer.",            "Sincronize antes de enviar.",              "Vor dem Senden synchronisieren."],
+        ["msg.send.connect.first"] = ["Connettiti al server e sincronizza prima di inviare.",             "Connect to the server and synchronize before sending.", "Conéctate al servidor y sincroniza antes de enviar.", "Connectez-vous au serveur et synchronisez avant d'envoyer.", "Conecte-se ao servidor e sincronize antes de enviar.", "Mit dem Server verbinden und vor dem Senden synchronisieren."],
+        ["msg.amount.invalid"]   = ["Importo non valido.",                                               "Invalid amount.",              "Importe no válido.",                   "Montant invalide.",                        "Valor inválido.",                          "Ungültiger Betrag."],
+        ["msg.feerate.invalid"]  = ["Fee rate non valido.",                                              "Invalid fee rate.",            "Tarifa no válida.",                    "Taux de frais invalide.",                  "Taxa inválida.",                           "Ungültige Gebührenrate."],
+        ["msg.broadcasted"]      = ["Trasmessa",                                                         "Broadcast",                    "Transmitida",                          "Diffusée",                                 "Transmitida",                              "Übertragen"],
+        ["msg.donate.thanks"]    = ["Grazie! txid",                                                      "Thank you! txid",              "¡Gracias! txid",                       "Merci ! txid",                             "Obrigado! txid",                           "Danke! txid"],
+        ["msg.unsigned.watchonly"] = [" · NON firmata (watch-only)",                                    " · NOT signed (watch-only)",   " · NO firmada (watch-only)",           " · NON signée (watch-only)",               " · NÃO assinada (watch-only)",             " · NICHT signiert (watch-only)"],
+        ["msg.cert.mismatch"]    = [
+            "Il certificato TLS di {0} è cambiato rispetto a quello salvato. Se il server ha rinnovato il certificato, esegui il reset dei certificati SSL.",
+            "The TLS certificate of {0} has changed from the one saved. If the server renewed its certificate, reset the SSL certificates.",
+            "El certificado TLS de {0} ha cambiado respecto al guardado. Si el servidor renovó su certificado, restablece los certificados SSL.",
+            "Le certificat TLS de {0} a changé par rapport à celui enregistré. Si le serveur a renouvelé son certificat, réinitialisez les certificats SSL.",
+            "O certificado TLS de {0} mudou em relação ao salvo. Se o servidor renovou o certificado, redefina os certificados SSL.",
+            "Das TLS-Zertifikat von {0} hat sich gegenüber dem gespeicherten geändert. Wenn der Server das Zertifikat erneuert hat, setzen Sie die SSL-Zertifikate zurück."],
 
         // Contacts
         ["contacts.name"]         = ["Nome",                                                              "Name",                         "Nombre",                               "Nom",                                      "Nome",                                     "Name"],