chore: Doc public API in the .h

[zfields]

Migrated and improved language of API documentation.

[Copilot]

Pull Request Overview

This PR consolidates public API documentation by moving it from the .cpp implementation file to the .h header file, making the documentation more accessible to users and tools that inspect header files.

Key Changes:

• Moved all Doxygen-style documentation blocks from Notecard.cpp to Notecard.h
• Updated some documentation descriptions to be more precise and consistent
• Removed redundant documentation from the implementation file

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/Notecard.h	Added comprehensive Doxygen documentation blocks for all public API methods
src/Notecard.cpp	Removed documentation blocks now present in the header file; updated one existing doc block for clarity

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