feat(transfer): add Send-tab guards, a correct TxID label + copy, inline reasons

The address-transfer dialog (own-address moves) enabled Confirm on amount alone,
so a disconnected / syncing / locked wallet failed only at submit. It now
mirrors the Send tab's guards (strictly more restrictive — the transfer logic is
unchanged) and re-checks live state before broadcast, shows an inline reason
when blocked (enter amount / not connected / syncing / locked), and labels the
result as a "Transaction ID" (not "Operation ID") with a copy button.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/util/i18n.cpp

@@ -1118,6 +1118,8 @@ void I18n::loadBuiltinEnglish()
         strings_["confirm_transfer"] = "Confirm Transfer";
         strings_["transfer_sent"] = "Transfer Sent";
         strings_["transfer_sent_desc"] = "Your transfer has been submitted to the network.";
+        strings_["transfer_txid_label"] = "Transaction ID: %s";
+        strings_["transfer_tooltip_locked"] = "Wallet is locked — unlock it to transfer";
         strings_["transfer_failed"] = "Transfer Failed";
         
         // Misc dialog strings