Support locking and unlocking of wallet while in use

The Issue

The latest SDK includes an account_lock function that we can use to lock a users wallet while they have the app open. This would be useful when allowing LBRY to run in the background, or when using LBRY in a public setting. I think it should also lock down any changes in the app (i.e. mature content setting/download directory/etc) and put a banner with something along the lines of "wallet is locked, please unlock by clicking here" across the top. When locked, new videos cannot be played, but existing ones should work.

System Configuration

• LBRY Daemon version:
• LBRY App version:
• LBRY Installation ID:
• Operating system:

Anything Else

Screenshots

Internal Use

Acceptance Criteria

Definition of Done

• Tested against acceptance criteria
• Tested against the assumptions of the user story
• The project builds without errors
• Unit tests are written and passing
• Tests on devices/browsers listed in the issue have passed
• QA performed & issues resolved
• Refactoring completed
• Any configuration or build changes documented
• Documentation updated
• Peer Code Review performed