Read legacy app's database, and migrate data

[AhmedTareek]

Fixes #1070

Changes:

• Transcribed decompression code from Kotlin to Dart.
• Transcribed migrations for both accounts and settings from the RN app.
• Added functionality to insert the obtained accounts and settings data into the app database upon creation.

Testing:

• Tested the decompression process.
• Tested the migrations for both settings and accounts.
• Tested the insertion of the obtained data into the app database.