Add bootstrap download dialog and fix 100 missing translation keys

- New BootstrapDownloadDialog accessible from Settings page
  - Stops daemon before download, prevents auto-restart during bootstrap
  - Confirm/Downloading/Done/Failed states with progress display
  - Mirror support (bootstrap2.dragonx.is)
- Add bootstrap_downloading_ flag to prevent tryConnect() auto-reconnect
- Right-align Download Bootstrap + Setup Wizard buttons in settings
- Add 100 missing i18n keys to all 8 language files (de/es/fr/ja/ko/pt/ru/zh)
  - Includes bootstrap, explorer, mining benchmark, transfer, delete blockchain,
    force quit, address label, and settings section translations
- Update add_missing_translations.py with new translation batch

src/app.h

@@ -273,6 +273,9 @@ public:
     void setUseEmbeddedDaemon(bool use) { use_embedded_daemon_ = use; }
     void rescanBlockchain();  // restart daemon with -rescan flag
     void deleteBlockchainData();  // stop daemon, delete chain data, restart fresh
+    bool stopDaemonForBootstrap(); // stop daemon + disconnect for bootstrap, returns true if was running
+    bool isBootstrapDownloading() const { return bootstrap_downloading_; }
+    void setBootstrapDownloading(bool v) { bootstrap_downloading_ = v; }
 
     // Get daemon memory usage in MB (uses embedded daemon handle if available,
     // falls back to platform-level process scan for external daemons)
@@ -542,6 +545,7 @@ private:
     // First-run wizard state
     WizardPhase wizard_phase_ = WizardPhase::None;
     std::unique_ptr<util::Bootstrap> bootstrap_;
+    bool bootstrap_downloading_ = false;  // true while settings bootstrap dialog is active
     std::string wizard_pending_passphrase_;  // held until daemon connects
     std::string wizard_saved_passphrase_;    // held until PinSetup completes/skipped