feat(ui): large-wallet nudge in Node & Security

The BDB wallet.dat bloats with shielded-note witness data and never shrinks
in place, so a mining/shielded wallet can grow past 500 MB. Below the Wallet
Size row, show a one-line amber hint once wallet.dat crosses 500 MB with a
"Consolidate notes…" shortcut that opens the Merge to Address (z_mergetoaddress)
dialog. Full-node only (lite has no wallet.dat here); threshold is a single
named constant. i18n keys fall back to English for non-English locales.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/util/i18n.cpp

@@ -667,6 +667,9 @@ void I18n::loadBuiltinEnglish()
         strings_["wiz_pin_mismatch"] = "PINs do not match";
         strings_["settings_data_dir"] = "Data Dir";
         strings_["settings_wallet_size_label"] = "Wallet Size";
+        strings_["wallet_size_warn"] = "This wallet file is large. Consolidating your notes can curb further growth.";
+        strings_["tt_wallet_size_warn"] = "Shielded wallets grow with each note's witness data — merging many notes into one address reduces it. Back up first.";
+        strings_["wallet_size_consolidate"] = "Consolidate notes\xE2\x80\xA6";
         strings_["settings_debug_changed"] = "Debug categories changed \xe2\x80\x94 restart daemon to apply";
         strings_["settings_auto_detected"] = "Auto-detected from DRAGONX.conf";
         strings_["settings_visual_effects"] = "Visual Effects";