feat(ui): large-wallet nudge as a one-time toast + clickable alert

Extend the wallet-bloat warning beyond the Settings banner: when wallet.dat
first crosses 500 MB (full-node, synced), fire a one-time warning toast plus a
clickable "Consolidate notes…" entry in the bell/alerts panel that opens Merge
to Address. The persisted large_wallet_warned flag keeps it once-only and
re-arms if the file later shrinks back under the threshold.

- AlertRecord gains an optional onClick + actionHint; Notifications::action()
  pushes a toast and a clickable history entry. renderAlertHistoryPanel() now
  renders the accent action link (under the message) and measures true content
  height so wrapped messages + the link aren't clipped.
- App::maybeWarnLargeWallet() (mirrors maybeRemindSeedBackup) runs once per
  launch from update(); reuses the existing wallet_size_warn/consolidate strings.

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

src/config/settings.cpp

@@ -232,6 +232,7 @@ bool Settings::load(const std::string& path)
         }
         loadScalar(j, "wizard_completed", wizard_completed_);
         loadScalar(j, "seed_backup_reminded", seed_backup_reminded_);
+        loadScalar(j, "large_wallet_warned", large_wallet_warned_);
         if (j.contains("empty_wallet_warning_acked") && j["empty_wallet_warning_acked"].is_array()) {
             empty_wallet_warning_acked_.clear();
             for (const auto& w : j["empty_wallet_warning_acked"])
@@ -506,6 +507,7 @@ bool Settings::save(const std::string& path)
     }
     j["wizard_completed"] = wizard_completed_;
     j["seed_backup_reminded"] = seed_backup_reminded_;
+    j["large_wallet_warned"] = large_wallet_warned_;
     j["empty_wallet_warning_acked"] = json::array();
     for (const auto& w : empty_wallet_warning_acked_)
         j["empty_wallet_warning_acked"].push_back(w);