Fix operator emails rejected in Operated By

Declaring operated_by at the procedure root prompts the operator on the identify-unit screen, where the field wrongly inherited the serial-number character check and rejected email addresses.

• Fixed the Operated By field rejecting emails and other free-text operator names on the identify-unit screen
• Fixed custom metadata values on the same screen being limited to the serial-number character set
• Added regression tests locking the identify-form validation to unit-identity fields only