BasyaNet 3.7.6 experimental account sync

Settings -> Advanced -> Experimental features -> BasyaNet Account

- Create an account or sign in to an existing account on a new desktop installation.
- Successful create/sign-in asks the configured Gmail transport to send a rate-limited thank-you email.
- Bookmarks, normal history, and theme are merged between signed-in installations.
- Browser sync data is AES-256-GCM encrypted before upload.
- Passwords are never stored as plaintext; authentication stores salted scrypt password hashes.
- Local browser data remains usable when sync is unavailable.
- Sync writes use explicit revisions and merge/retry rather than silently overwriting another installation.
- Deleting a cloud account invalidates its sessions while leaving local bookmarks/history/theme intact.
