feat: Add trusted devices with auto-accept functionality

[capynet]

Summary

• Added ability to trust devices for automatic file acceptance within a configurable timeout
• New callout banner appears when receiving files from new/expired devices with options:
  • "Yes, trust" - adds device to trusted list
  • "Don't ask again" - blocks device from future prompts
• Added Settings > Devices section to manage trusted and blocked devices
• Trusted devices show countdown timer "Expires in Xm Ys"
• System notifications are suppressed for auto-accepted transfers from trusted devices
• Expired trusted devices are automatically cleaned up

Trusted devices

No trusted devices

Features

• Configurable auto-accept timeout (1, 5, 10, 60 minutes)
• Persistent storage for trusted and blocked devices
• Real-time countdown updates in settings
• Automatic cleanup of expired devices

Test plan

• Send file from new device, verify trust callout appears
• Click "Yes, trust" and send another file within timeout, verify auto-accept
• Check Settings > Devices shows trusted device with countdown
• Wait for timeout and verify device is removed
• Test "Don't ask again" blocks future prompts
• Verify blocked devices can be unblocked from Settings

Closes #384