Allow use offline when logged in to Orca Cloud (#14235)

* Store user session information along with refresh token, to allow offline use once user is logged in

* Don't bother with avatar because we won't see it when offline anyway

* Fix offline Sync Presets freezing the UI on repeat clicks

Ignore restart_sync_user_preset() while a manual sync's progress dialog is on screen, so a second app-modal dialog can't stack on the first. Offline the dialog blocks on a long, uncancellable HTTP timeout; on macOS the global menu stays live while the window is disabled, so a second click otherwise wedges the app (force-quit only).

* Skip redundant user-secret re-write on startup

set_user_session() always re-encrypts and writes the secret to disk; on the startup restore path that just rewrites the bytes it was loaded from. Add a persist flag so the restore path skips it. Also drop an unused catch binding and a stray blank line.

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Co-authored-by: SoftFever <softfeverever@gmail.com>

src/slic3r/GUI/GUI_App.hpp

@@ -323,6 +323,7 @@ private:
     boost::thread    m_sync_update_thread;
     std::shared_ptr<int> m_user_sync_token;
     std::atomic<bool>    m_restart_sync_pending {false};
+    std::atomic<bool>    m_sync_user_preset_dlg_active {false}; // a manual "Sync Presets" progress dialog is on screen (see restart_sync_user_preset)
     std::atomic<bool>    m_sync_user_presets_now {false}; // request the sync loop to push user presets on its next tick
     std::atomic<bool>    m_migration_retry_pending {false};
     bool             m_is_dark_mode{ false };