fix: add applies_to to numbering series

[Nimble-Momonga]

QUI-9815

[talken]

Task linked: QUI-9815 [Doc number] [BE] Adjust endpoint to create and edit number series in Public API
Task linked: QUI-9987 [Doc number] [BE] Handle Logging whenever a “new_documents” series is converted to historical

[Copilot]

Pull request overview

This PR adds the applies_to field to the numbering series API documentation. The field is marked as REQUIRED and accepts values of "existing" or "new" to indicate whether a numbering series applies to existing or new documents. Additionally, it includes a spelling fix changing "fronted" to "frontend".

Changes:

• Added applies_to attribute to the attributes table with description and accepted values
• Updated all example JSON responses to include the applies_to field
• Added applies_to filter to the available filters documentation
• Added documentation about update restrictions for the applies_to field

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