Legacy desktop wallet account migration

[smk762]

Updated by @CharlVS based on the recent UX audit by @gcharang

Updates from recent UX audit

• Cover migration edge‑cases: (a) user already has a corresponding HD wallet; (b) duplicate seed imported previously under a different wallet name.
• Allow selecting a target wallet or creating a new one, and warn about swap history and address‑book implications.

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With the sunset of the Legacy Desktop Wallet, an influx of users will be moving their logins to the new apps.
To make this transition as low friction as possible, it would help to have a way that the old wallet's encrypted seed files could be imported into the new apps.

Unfortunately these were encrypted a bit differently.

I can provide an existing seedfile and password for testing.

Additionally, users have requested the import/export of:

• maker orders
• makerbot configs
• addressbooks
• swap histories

Additionally, migration of user's data should also be possible via a button and file/folder dialog, so seeds can be selected for import. Legacy desktop app would store these in

• Windows: C:\Users\USERNAME\AppData\Roaming\atomic_qt
• OSX: ~/Library/Application Support/AtomicDEX Desktop
• Linux: ~/.atomic_qt

[CharlVS]

@smk762 please provide the sample data to me via DM. At the very least, we'll cover seed import/export, but please send over everything.

[smk762]

@CharlVS please be aware that the legacy wallet seed files being decrypted contain the complete MM2.json, not just the passphrase/seed