daemon version check, idle mining control, bootstrap mirror, import key paste, and cleanup

- Add startup binary version checking for dragonxd/xmrig
- Display daemon version in UI
- Add idle mining thread count adjustment
- Add bootstrap mirror option (bootstrap2.dragonx.is) in setup wizard
- Add paste button to import private key dialog with address validation
- Add z-address generation UI feedback (loading indicator)
- Add option to delete blockchain data while preserving wallet.dat
- Add font scale slider hotkey tooltip (Ctrl+Plus/Ctrl+Minus)
- Fix Windows RPC auth: trim \r from config values, add .cookie fallback
- Fix connection status message during block index loading
- Improve application shutdown to prevent lingering background process

src/util/bootstrap.h

@@ -51,6 +51,7 @@ public:
 
     /// Base URL for bootstrap downloads (zip + checksum files).
     static constexpr const char* kBaseUrl = "https://bootstrap.dragonx.is";
+    static constexpr const char* kMirrorUrl = "https://bootstrap2.dragonx.is";
     static constexpr const char* kZipName = "DRAGONX.zip";
 
     /// Start the bootstrap process on a background thread.