Fix TypeScript issues in device-management.ts and unlinked_books.ts:
1. device-management.ts:
- Move 'deviceType' variable declaration to function scope in showDeviceSettings()
- Previously declared inside a Promise chain, creating potential scope issues
- Now properly declared at function level before async operations
2. unlinked_books.ts:
- Remove unused 'result' parameter from .then() handlers
- Fixes autoLinkBook() and confirmManualLink() functions
- Handlers don't use the API response result, only need success/failure
These changes improve code clarity and resolve potential runtime issues
with variable accessibility in async callback chains.
Technical details:
- deviceType: moved from Promise .then() block to function scope
- Unused parameters: removed to prevent linting warnings and improve clarity