Add documentation for the option to universal search by register ID without scope

[aviv-nd]

Closes northdata/northdata#13774

[Copilot]

Pull Request Overview

This PR adds documentation for the universal search feature to clarify that users can search by register ID without specifying the scope (e.g., city) in countries where register IDs are not unique identifiers.

Key Changes:

• Corrected grammar in the universal search description
• Added footnote explaining register ID search flexibility

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[Copilot]

[nitpick] The footnote explanation is verbose and could be more concise. Consider rephrasing to: 'Register IDs can be searched without scope (e.g., city) even in countries where they aren't unique identifiers, returning all matching results.'

Suggested change

	\* It is possible to search only for the register ID even in countries where it isn't a unique identifier (e.g.,
	"HRB 2000" in Germany without the city) to look for all possible matches for that register ID.
	\* Register IDs can be searched without scope (e.g., city) even in countries where they aren't unique identifiers, returning all matching results.

[spinetrak]

LGTM