Three new sections inserted into <OpcUaEndpointEditor>:
1. Authentication (between the existing Connection row and Timing)
- 'Enable Authentication' button when Config.UserIdentity is null
- TokenType select (Anonymous / UsernamePassword / X509Certificate)
- Conditional Username + Password inputs for UsernamePassword
- Conditional Certificate path + Certificate password for X509Certificate
- 'Remove Authentication' button
2. Advanced subscription (after the existing Subscription row)
- Subscription display name (text)
- Subscription priority (number 0-255)
- Timestamps to return (Source / Server / Both select)
- Discard oldest (checkbox)
3. Deadband filter (after Advanced subscription)
- 'Enable Deadband' button when Config.Deadband is null
- Type select (Absolute / Percent), Value number input
- 'Remove Deadband' button
EnableAuthentication and EnableDeadband helpers complement EnableHeartbeat.
All new fields use the existing RenderFieldError helper for validator errors.
82/82 CentralUI tests pass (the 10 new editor tests drove the design).